Immunology

277

A selection of interesting papers that were published inthe two months before our press date in major journalsmost likely to report significant results in immunology.

• of special interest•• of outstanding interest

Current Opinion in Immunology 2002, 14:277–287

Selected by Tim ElliottUniversity of Southampton, Southampton, UK

e-mail: [email protected]

•• Disulfide bond isomerisation and the assembly of MHCclass I-peptide complexes. Dick TP, Bangia N, Peaper DR,Cresswell P: Immunity 2002, 16:87-98.Significance: Newly synthesised MHC class I moleculesassemble within the endoplasmic reticulum (ER) and load withoptimal peptides while bound to the transporter associatedwith antigen processing (TAP), tapasin, the oxidoreductaseERp57 and calreticulin: collectively these are called the peptide-loading complex (PLC). This is the first study of thefunction of ERp57 in this complex.Findings: By trapping disulphide-bonded intermediatesformed between ERp57 and other components of the PLC,using the sulphydryl blocker N-ethyl maleimide, the authorsfound that all ERp57 in the PLC was disulphide-bonded totapasin, although only a fraction of tapasin was bound toERp57. Formation of this ERp57–tapasin complex dependedon the presence of class I heavy chain (HC). Site-directedmutagenesis identified cysteine 95 of tapasin and cysteine 57of ERp57 as being required for forming the complex. Althoughno S–S intermediate was identified between ERp57 and HC,mutant tapasin molecules that did not bind to ERp57 restoredMHC class I expression when introduced into tapasin-nullcells. However, the class I molecules that were assembled inthese cells were less stable, and loading with optimal peptideswas impaired as a direct result of the failure of an intramolecularS–S (presumably in the α2 domain) to become fully oxidisedupon assembly.

•• Assembly and antigen presenting function of MHC class Imolecules in cells lacking the ER chaperone calreticulin.Gao B, Adhikari R, Howarth M, Nakamura K, Gold MC, Hill AB,Knee R, Michalak M, Elliott T: Immunity 2002, 16:99-110.Significance: This is the first study of the specific function ofcalreticulin in MHC class I assembly.Findings: Using a calreticulin-null cell line, the authors showedthat in the absence of calreticulin, MHC class I assembly wasnormal but loading with optimal peptides was severely impaired.Suboptimally loaded class I molecules in these cells were notsubjected to normal quality control (that is to say, retention in theER) but were released rapidly from the ER as unstable mole-cules that fall apart at or en route to the cell surface. As a result,the presentation of endogenous antigens to cytotoxic T lympho-cytes was dramatically impaired. Even in the absence ofcalreticulin, class I molecules were recruited to the PLC efficiently, along with ERp57 and tapasin. The function of calreticulin in antigen processing could not be substituted by asoluble construct of its ortholog calnexin in calreticulin-null cells.

• Recruitment of MHC class I molecules by tapasin into thetransporter associated with antigen processing complex isessential for optimal peptide loading. Tan P, Kropshofer H,Mandelboim O, Bulbuc N, Hammerling GJ, Momburg F:Eur J Immunol 2002, 168:1950-1960.Significance: This study helps relate the structure of tapasin toits function as a facilitator of optimal peptide loading of MHCclass I molecules.Findings: Various mutant tapasin molecules were introduced intoa tapasin-null cell in order to evaluate their ability to restore nor-mal peptide-loading of a human class I molecule (HLA-B*4402).Murine tapasin is poor at restoring peptide-loading (evaluated bymeasuring class I stability at 37°C versus 4°C; and by measuringthe life-span of B*4402 in transfected cells). A murine–humanchimeric molecule in which the first 149 amino acids of humantapasin were replaced by the mouse sequence improved peptide-loading to the level achieved by human tapasin lacking itstransmembrane domain (a construct lacking the carboxy-terminal49 amino acids); however, this was still significantly less efficientthan wild-type tapasin. No change in transport kinetics of class Imolecules out of the ER was seen for any of the mutants. Slightdifferences in peptide repertoire loaded onto class I were identified both biologically (using NK cell lines) and biochemically(mass spectroscopic analysis of eluted peptides). Interestingly,although only wild-type tapasin could recruit all members of thePLC effectively, normal levels of ERp57 (but not HC or calretic-ulin) were recruited to the PLC by mouse tapasin. This couldreflect the conservation of cysteine residues between the humanand mouse sequences (see Dick et al., above).

•• Tapasin is retained in the endoplasmic reticulum bydynamic clustering and exclusion from endoplasmic reticulum exit sites. Pentcheva T, Spiliotis ET, Edidin M:J Immunol 2002, 168:1538-1541.Significance: This study addresses the mechanism by whichtapasin is retained in the ER, where it performs an importantrole in assisting the loading of MHC class I molecules withoptimal peptides.

ImmunologyPaper alert

Contents (chosen by)

277 Antigen processing and recognition (Elliott)278 Innate immunity (Bonneville)278 Lymphocyte development (Zúñiga-Pflücker)279 Tumour immunology (Walker)280 Lymphocyte activation and effector functions (Essayan)281 Immunity to infection (Glaichenhaus and Vyakarnam)283 Immunogenetics (Casanova)284 Immunotherapy (Liu)284 Transplantation (Auchincloss, Waneck and LeGuern)285 Allergy and hypersensitivity (Akdis)286 Autoimmunity (Green)

Antigen processing and recognition

Findings: Using tapasin amino-terminally tagged with cyan- oryellow-fluorescent protein and fluorescence microscopy (combining deconvolution fluorescence microscopy, fluores-cence resonance energy transfer [FRET] and fluorescencerecovery after photobleaching [FRAP]) this study shows thattapasin does not reach the medial Golgi nor does it recyclebetween the ER and the ER-to-Golgi-intermediate compart-ment (ERGIC). Instead it is excluded from ER exit sites and ispresumably not recognised as cargo by the ER exit machinery.Despite its exclusion from these sites, tapasin is freely diffusible, suggesting that it is not retained via its inclusion in alarge protein matrix.

Selected by Marc BonnevilleInstitut de Biologie, Nantes, France


• Macrophage migration inhibitory factor (MIF) sustainsmacrophage proinflammatory function by inhibiting p53:regulatory role in the innate immune response. Mitchell RA,Liao H, Chesney J, Fingerle-Rowson G, Baugh J, David J,Bucala R: Proc Natl Acad Sci USA 2002, 99:345-350.Significance: This study describes a previously unrecognized butimportant mechanism that underlies the proinflammatory action ofMIF through regulation of macrophage viability and survival.Findings: MIF is known to regulate macrophage-mediatedinflammation and septic shock in response to endotoxin,through mechanisms that are yet unclear. The following observations indicate that MIF sustains macrophage survivaland function by suppressing activation-induced, p53-depen-dent apoptosis. Macrophages from MIF-deficient mice showenhanced apoptosis and decreased proinflammatory functionin response to endotoxin. Inhibition of p53 suppresses thisenhanced apoptosis and restores inflammatory function ofMIF-deficient macrophages. In addition MIF inhibitsp53-dependent apoptosis through induction of arachidonicacid metabolism and cyclooxygenase-2 expression.

• Reciprocal activating interaction between natural killercells and dendritic cells. Gerosa F, Baldani-Guerra B, Nisii C,Marchesini V, Carra G, Trinchieri G: J Exp Med 2002,195:327-333.• Contact-dependent stimulation and inhibition of dendriticcells by natural killer cells. Piccioli D, Sbrana S, Melandri E,Valiante NM: J Exp Med 2002, 195:335-341.• Human dendritic cells activate resting natural killer (NK)cells and are recognized via the NKp30 receptor by activated NK cells. Ferlazzo G, Tsang ML, Moretta L, Melioli G,Steinman RM, Münz C: J Exp Med 2002, 195:343-351.Significance: These studies demonstrate for the first time abidirectional cross-talk between NK cells and dendritic cells(DCs) that is probably relevant to the regulation of both innateand adaptive immune responses.Findings: In the study of Gerosa et al., mature DCs triggerexpression of activation markers and cytolytic activity of freshlyisolated NK cells. Fresh and activated NK cells respectivelyenhance and induce DC maturation and IL-12 production, andpotentiate the ability of DCs to stimulate allogeneic naiveT cells. Within peripheral blood lymphocytes, the reciprocalactivating interaction with DCs is restricted to NK cells. Piccioli

and colleagues show in addition that interactions between activated human NK cells and autologous immature DCs at alow NK:DC ratio (1:5) dramatically amplify DC cytokine production, in a manner dependent on cell-to-cell contact andTNF-α . At a high NK:DC ratio (5:1), DC functions are inhibitedbecause of killing by the autologous NK cells. Finally Ferlazzoet al. find that both immature and mature DCs trigger the proliferation, IFN-γ production and cytolytic function of fresh NKcells. In turn, activated NK cells kill immature, but not mature,DCs. The NK activating signal involves prominently but notexclusively the NKp30 natural cytotoxicity receptor.

• Human macrophage activation programs induced by bacterial pathogens. Nau GJ, Richmond JFL, Schlesinger A,Jennings EG, Lander ES, Young RA: Proc Natl Acad Sci USA2002, 99:1503-1508.Significance: This study brings the first comprehensive pictureof the macrophage activation program elicited by various bacteria and provides new insights into the pathogenesis ofmycobacterial infections.Findings: Expression of 6800 genes was monitored with highdensity DNA microarrays in macrophages exposed in vitro tomycobacteria, Gram-positive bacteria or Gram-negative bacteria. A shared transcriptional program involving around200 genes was elicited by all bacteria, and turned out to beinduced by Toll-like receptor agonists such as lipopolysaccharide,lipoteichoic acid and heat shock proteins. Pathogen-specificregulation of several genes was also apparent. In particular,M. tuberculosis induced little IL-12 and IL-15 relative to otherbacteria, and repressed IL-12 production. Since IL-12 — a keyinducer of proinflammatory T helper responses — is critical forhost resistance to tuberculosis, its inhibition by mycobacteriacould represent an escape mechanism allowing the bacteria tosurvive within macrophages.

Selected by Juan Carlos Zúñiga-PflückerDepartment of Immunology, University of Toronto, Toronto, Canada


•• BH3-only Bcl-2 family member Bim is required for apoptosis of autoreactive thymocytes. Bouillet P, Purton JE,Godfrey DI, Zhang LC, Coultas L, Puthalakath H, Pellegrini M,Cory S, Adams JM, Strasser A: Nature 2002, 415:922-926.Significance: The mechanisms regulating the induction of pro-grammed cell death during thymocyte negative selection havenot been fully elucidated. This study shows that thymocytes fromBim-deficient mice are refractory to apoptosis signals inducedby TCR stimulation, indicating that this pro-apoptotic member ofthe Bcl-2 family is involved in mediating negative selection.Findings: When compared with thymocytes from wild-typemice, Bim-deficient thymocytes showed a dramatic resistanceto several apoptosis-inducing stimuli, such as anti-TCR engage-ment, and exposure to bacterial or endogenous superantigens.Bim-deficient thymocytes from two distinct TCR-transgenicmouse strains also showed a defect in their ability to undergoclonal deletion when exposed to otherwise apoptosis-inducingantigens. One potential mechanism by which Bim may mediateits pro-apoptotic function was suggested, as TCR ligation onthymocytes induced Bim expression, which may then interactwith Bcl-XL to inhibit the latter’s anti-apoptotic function.

278 Paper alert

Innate immunity

Lymphocyte development

• Helix-loop-helix proteins regulate pre-TCR and TCR signaling through modulation of Rel/NF-κκB activities.Kim D, Xu M, Nie L, Peng XC, Jimi E, Voll RE, Nguyen T,Ghosh S, Sun XH: Immunity 2002, 16:9-21.Significance: The HLH transcription factors E2A and HEB areknow to be important in lymphocyte development; however,their ability to influence pre-TCR and/or TCR signaling has notbeen previously appreciated. Surprisingly, this study shows thatNF-κB activity is strongly induced in the absence of E2A/HEBfunction, which results in a disruption of the normal differentia-tion outcomes following pre-TCR or TCR signaling.Findings: Thymocyte differentiation in transgenic mice express-ing the HLH inhibitors Id1 and Tal1 was shown to be blocked ata very early stage (DN1→DN2); these thymocytes were alsoshown to be undergoing apoptosis. In contrast, thymocytes fromRAG-deficient mice expressing the Id1 transgene were able to differentiate to the CD4+CD8+ (DP) stage; however, inRAG-deficient mice expressing higher levels of the Id1 trans-gene differentiation to the DP stage was not observed.Surprisingly, thymocytes from Id1 or Tal1 transgenic miceshowed a dramatic increase in NF-κB activity and, in particular,highly elevated levels of c-Rel and p50. To further demonstratean interplay between a lack of HLH function and increasedNF-κB activity in mediating a block in early thymocyte develop-ment, Kim et al. crossed the Id1 transgenic mice with eitherIKKβ (constitutively active to increase NF-κB activity) or IκBα(superinhibitor mutant to decrease NF-κB activity) transgenicmice, resulting in an exacerbation or a rescue of the develop-mental block, respectively. This study also shows that signalsthat mimic pre-TCR function result in a transient reduction ofE2A/HEB binding activity, probably by inducing the expressionof Id family members. How NF-κB activity is modulated in theabsence of HLH function is not clear; however, the fact thatthese transcription factors can regulate the outcome of pre-TCRsignaling presents a novel insight into the regulation of early thymocyte development by modulating HLH and NF-κB activity.

• Deltex1 redirects lymphoid progenitors to the B cell lineage by antagonizing Notch1. Izon DJ, Aster JC, He Y,Weng A, Karnell FG, Patriub V, Xu L, Bakkour S, Rodriguez C,Allman D, Pear WS: Immunity 2002, 16:231-243.Significance: Notch1 receptor signaling has been implicated inthe cell fate decision of lymphoid progenitors, in which Notch1activation promotes T cell development, whereas in its absenceB cell differentiation is favored. However, mechanisms that mayregulate Notch1 function in lymphoid progenitors have notbeen fully characterized. This study shows that Deltex1 canantagonize Notch1-dependent transcriptional activity, revealingyet another layer of complexity in the regulation of Notch1 signals during lymphocyte lineage commitment.Findings: Mice reconstituted with bone-marrow (BM)-derivedhematopoietic progenitors that have been retrovirally inducedto overexpress Deltex1 develop normal levels of B cells in theperiphery and BM, whereas T cells are absent in the peripheryand severely reduced in the thymus. Instead of efficient T celllymphopoiesis, the thymus of mice reconstituted withDeltex1-overexpressing BM cells contained an increased proportion of B cells. Similar results were obtained whenDeltex1-overexpressing fetal-liver-derived hematopoietic progenitors were used to reconstitute fetal thymic organ cultures — B cells developed at the expense of T cells in the thymus. Izon et al. also show that Deltex1 may not only antagonizethe function of the Notch1 transcriptional activation domain, but

also augment E2A activity, providing an attractive explanationfor effects of enforced Deltex1 expression.

•• PU.1 regulates expression of the interleukin-7 receptorin lymphoid progenitors. DeKoter RP, Lee HJ, Singh H:Immunity 2002, 16:297-309.•• Constitutive expression of PU.1 in fetal hematopoieticprogenitors blocks T cell development at the pro-T cellstage. Anderson MK, Weiss AH, Hernandez-Hoyos G,Dionne CJ, Rothenberg EV: Immunity 2002, 16:285-296.Significance: The Ets family transcription factor PU.1 isrequired for the development of lymphoid and myeloid cell lineages. These studies point to two different functions for theregulated expression of PU.1 during B cell and T cell differenti-ation. In one instance, the study by DeKoter et al. reveals thatPU.1 is an important regulator of the IL-7 receptor (IL-7R)αgene expression, providing a rationale for the block in B celldevelopment seen in PU.1-deficient mice. On the other hand,Anderson et al. show that enforced overexpression of PU.1expression during thymocyte development resulted in an earlyblock in T cell differentiation, and suggest that unregulatedPU.1 expression allows for myeloid cell lineage specification bythymocyte progenitors. Taken together, these recent reportshighlight the importance of the correct temporal expression,dose, and lineage specific expression of PU.1 for the differenti-ation of myeloid and lymphoid lineages.Findings: The first study shows that PU.1 deficient hematopoieticprogenitors fail to express transcripts for IL-7Rα. To directly testwhether lack of IL-7Rα expression is responsible for the inability ofPU.1-deficient progenitors to give rise to B cells, hematopoieticprogenitors from PU.1-deficient mice were retrovirally transducedto express IL-7Rα. Indeed, enforced expression of IL-7R rescuedB cell differentiation from PU.1-deficient progenitors. The secondstudy addresses whether the developmentally regulated expres-sion of PU.1 during thymocyte development is essential forprecursors to differentiate beyond the pro-T cell stage. Fetalthymic organ cultures reconstituted with retrovirally transducedfetal liver progenitors overexpressing PU.1 showed a completeblock in early thymocyte development. However, myelopoiesiswas unaffected in PU.1-overexpressing progenitors. In this regard,transient overexpression of PU.1 in fetal thymocytes revealed thatseveral myeloid lineage-specific gene products could be inducedin CD90+ thymocyte progenitors.

Selected by Paul R WalkerUniversity Hospital Geneva, Geneva, Switzerland


• CD94-NKG2A receptors regulate antiviral CD8+ T cellresponses. Moser JM, Gibbs J, Jensen PE, Lukacher AE:Nat Immunol 2002, 3:189-195.Significance: Inhibitory NK cell receptors such as those of theCD94–NKG2 family can also be expressed by T cells, some ofwhich have been shown to be specific for tumour-associatedantigens. It has been an attractive hypothesis, based mainly onin vitro data, that such expression may explain inefficaciousantitumour responses. This study moves closer to the in vivosituation and describes how antiviral CTL responses and sus-ceptibility to outgrowth of virus-induced tumours are associatedwith expression of CD94–NKG2A on antigen-specific CTLs.

Paper alert 279

Tumour immunology

Findings: Using the highly oncogenic mouse polyoma virusmodel, virus-specific CTLs (detected by MHC–peptide fluores-cent multimers) were assessed in polyoma-virus-infected mice.CD94–NKG2 was induced on virus-specific CTLs duringin vivo infection and was inversely correlated with cytotoxicityassessed ex vivo. When CBA/J mice (susceptible to polyoma-virus-induced tumours) were infected neonatally with polyomavirus, there was a lower magnitude antiviral response, retardedviral clearance, but an elevated proportion of CD94–NKG2-positive cells. The ex vivo inhibition of specific cytotoxicity byCD94–NKG2 could be reversed by blockade or endocytosis ofits ligand, Qa-1b.

• Tumor growth enhances cross-presentation leading tolimited T cell activation without tolerance. Nguyen LT,Elford AR, Murakami K, Garza KM, Schoenberger SP,Odermatt B, Speiser DE, Ohashi PS: J Exp Med 2002,195:423-435.Significance: The spectre of tumour-induced tolerance is frequently invoked as an obstacle for the development of efficacious tumour vaccines. Data from this study by Nguyenet al. in a spontaneous tumour model demonstrate that tolerance induction is not inevitable, even in the face of hightumour burden. The outcome of immune activation versus tolerance may be influenced by factors such as the proliferationrate of the tumour and the balance between cross-presentationand direct presentation of tumour-associated antigens.Findings: Using double transgenic mice spontaneously developing insulinomas expressing lymphocytic choriomeningitisvirus glycoprotein (LCMV-GP), specific CTLs were inducedand proliferated in correlation with increasing tumour burden.The CTLs were functional, high avidity cells and were activatedby cross-presentation. However, even in mice with elevated levels of LCMV-GP-specific CTL precursors (resulting fromcrossing with mice transgenic for an LCMV-GP-specific TCR),only a modest delay in tumour formation (assessed by hypogly-caemia) was noted. More substantial in vivo antitumour effectorfunction was achieved by vaccination with LCMV-GP peptideand agonistic CD40 antibody, or by infection with LCMV orrecombinant vaccinia virus expressing LCMV-GP.

• Antitumor monoclonal antibodies enhance cross-presentation of cellular antigens and the generation ofmyeloma-specific killer T cells by dendritic cells.Dhodapkar KM, Krasovsky J, Williamson B, Dhodapkar MV:J Exp Med 2002, 195:125-133.Significance: The protective effect of tumour-specific mono-clonal antibodies has in some cases been defined to be CD8dependent, but with ill-defined mechanisms. Here, Dhodapkaret al. show that antibodies binding specifically to tumour cellspotentiate cross-presentation of tumour antigens to CTLs by dendritic cells (DCs) via an Fcγ receptor dependent mechanism. Thissuggests possibilities for optimising antibody- and CTL-mediatedimmunotherapies as well as understanding the potential implica-tions of naturally occurring antitumour antibodies in patients.Findings: Myeloma cell lines (live, apoptotic or necrotic)expressing various tumour-associated antigens were coatedwith monoclonal antibody specific for syndecan-1 (expressed onthe myeloma cell surface) or an IgG1 isotype control antibody.They were then fed to HLA-mismatched, monocyte-derivedimmature DCs. Similar phagocytic uptake of tumour cells wasnoted for all categories of treated tumour cells, but phagocyto-sis resulted in only partial maturation. After complete maturation

in a standard cytokine cocktail, mature DCs were then coculturedwith autologous T cells. Cross-priming, specific for antigens present on the phagocytosed tumour cells, was most efficientwhen DCs had engulfed syndecan-1-coated tumour cells andwas reduced when DCs were preincubated with Fc-receptor-specific antibodies.

• Increased susceptibility to tumor initiation and metastasisin TNF-related apoptosis-inducing ligand-deficient mice.Cretney E, Takeda K, Yagita H, Glaccum M, Peschon JJ,Smyth MJ: J Immunol 2002, 168:1356-1361.• Critical role for tumor necrosis factor-related apoptosis-inducing ligand in immune surveillance against tumordevelopment. Takeda K, Smyth MJ, Cretney E, Hayakawa Y,Kayagaki N, Yagita H, Okumura K: J Exp Med 2002,195:161-169.Significance: Recent advances have highlighted the role of NKcells in tumour immune surveillance. One defined effector molecule of NK cells is TNF-related apoptosis-inducing ligand(TRAIL), a cytokine with potent antitumour cytotoxic function.These papers present evidence suggesting that endogenouslyproduced TRAIL plays an important role in protecting againstspontaneous tumour formation and metastasis.Findings: Both of these studies analyse tumour formationin vivo, either in TRAIL deficient mice (Cretney et al.) or in micein which endogenously produced TRAIL is neutralised by antibodies (Takeda et al.). Certain results in the knockout miceconfirm previous findings with neutralising antibodies (the contribution of TRAIL to NK-cell-mediated suppression of exper-imental RENCA metastases to the liver), but the results gofurther and show that TRAIL is also important in the control ofthe spontaneously metastasising 4T1 mammary carcinoma andin the outgrowth of methylcholanthrene (MCA)-induced fibrosar-comas. The latter findings were also confirmed with anti-TRAILantibody. Furthermore, spontaneously developing tumours inp53+/– mice appeared more rapidly and frequently in TRAIL-neutralised mice; these tumours were also highly sensitive toTRAIL in vitro compared with those arising in non-treated mice.

Selected by David EssayanUS Food and Drug Administration, Rockville, MD, USA


• The absence of interleukin 9 does not affect the develop-ment of allergen-induced pulmonary inflammation norairway hyperreactivity. McMillan SJ, Bishop B, Townsend MJ,McKenzie AN, Lloyd CM: J Exp Med 2002, 195:51-57.• Pulmonary overexpression of IL-9 induces Th2 cytokineexpression leading to immune pathology. Temann U-A,Ray P, Flavell RA: J Clin Invest 2002, 109:29-39.Significance: IL-9 is sufficient but not obligatory for the devel-opment of pulmonary pathology in murine models of asthma.Findings: McMillan et al. demonstrate that IL-9 knockout mice(BALB/cJ background) that were sensitized to ovalbumin devel-oped pulmonary eosinophilia, airway hyper-reactivity and gobletcell hyperplasia to a similar degree as their wild-type littermates.IgE production and levels of IL-4, IL-5 and IL-13 from BAL werealso comparable in the knockout and wild-type mice. Temannet al. demonstrate that pulmonary overexpression of IL-9 usingan inducible transgenic model resulted in lymphocytic and

280 Paper alert

Lymphocyte activation and effector functions

eosinophilic infiltration, epithelial cell hypertrophy, enhancedmucin staining, mast cell hyperplasia, and generation of IL-4,IL-5 and IL-13. Blockade of IL-4 or IL-5 decreased airwayeosinophilia without affecting mucous hypersecretion, whereasneutralization of IL-13 decreased both parameters.

• I-κκB kinase ββ is critical for B cell proliferation and antibody response. Ren H, Schmalstieg A, Yuan D,Gaynor RB: J Immunol 2002, 168:577-587.Significance: Since I-κB kinase β (ΙΚΚβ)-deficient mice diein utero, its role in B cell development had to be assessed intransgenic mice using a dominant negative (DN) constructunder the control of the IgH promoter/enhancer.Findings: The DN construct altered NF-κB activation to variousstimuli without altering the expression of NF-κB subunits orIKKα. B cells from these mice developed normal surface markerprofiles, but failed to proliferate appropriately to various stimuli;the proliferative defect was not due to enhanced apoptosis.Finally, despite relatively normal basal antibody production,these mice demonstrated impaired antibody production inresponse to specific antigens.

• IL-2 and related cytokines can promote T cell survival byactivating AKT. Kelly E, Won A, Refaeli Y, Parijs LV: J Immunol2002, 168:597-603.Significance: Description of a common signaling element forthe promotion of T cell survival by the IL-2 family of cytokines.Findings: IL-2, IL-4, IL-7 and IL-15 each induced phosphoryla-tion of Ser473 on AKT. Expression of activated AKT led tosurvival and expansion of antigen-primed T cells followinggrowth factor withdrawal. Although expression of activated AKTdid not protect T cells from activation-induced cell death,expression was associated with upregulation of Bcl-2.

• Stimulation of CD25+CD4+ regulatory T cells throughGITR breaks immunological self-tolerance. Shimizu J,Yamazaki S, Takahashi T, Ishida Y, Sakaguchi S: Nat Immunol2002, 3:135-142.Significance: Glucocorticoid-induced tumor necrosis factorreceptor family-related gene (GITR, or TNFRSF18) is a selective, negative regulator of T regulatory cells.Findings: GITR is highly expressed on T regulatory cells in thethymus and periphery. A monoclonal antibody specific for GITRupregulated NF-κB transcription and abrogated CD25+CD4+

T cell mediated suppression in a dose dependent manner; thisactivity was not seen with the Fab fragment. Adoptive transferof GITR-depleted splenocytes or in vivo stimulation of GITRwas associated with the induction of autoimmunity.

• Reciprocal activating interaction between natural killercells and dendritic cells. Gerosa F, Baldani-Guerra B, Nisii C,Marchesini V, Carra G, Trinchieri G: J Exp Med 2002,195:327-333.• Contact-dependent stimulation and inhibition of dendriticcells by natural killer cells. Piccioli D, Sbrana S, Melandri E,Valiante NM: J Exp Med 2002, 195:335-341.• Human dendritic cells activate resting natural killer (NK)cells and are recognized via the NKp30 receptor by activated NK cells. Ferlazzo G, Tsang ML, Moretta L, Melioli G,Steinman RM, Münz C: J Exp Med 2002, 195:343-351.• Dendritic and natural killer cells cooperate in the control/switch of innate immunity. Zitvogel L: J Exp Med2002, 195:F9-F14.

Significance: A collection of papers and a commentarydescribing reciprocal interactions between dendritic cells(DCs) and NK cells.Findings: Gerosa et al. demonstrated both enhancedNK-cell-mediated cytotoxicity upon activation in the presence ofDCs as well as enhanced DC activation/maturation in the pres-ence of NK cells. Piccioli et al. showed that resting NK cellsinduced cell-dose-dependent activation/maturation of DCs byboth cognate and non-cognate (TNF-mediated) mechanisms.Interestingly, activated NK cells induced DC activation at lowNK:DC ratios and DC inhibition at high NK:DC ratios. Ferlazzoet al. demonstrated that low numbers of immature or matureDCs were capable of inducing NK cell activation, proliferationand effector functions. Interestingly, the latter two manuscriptsalso provided data suggesting DC killing by NK cells.

Selected by Nicolas GlaichenhausInstitut de Pharmacologie Moléculaire et Cellulaire, Valbonne, France


•• Pathogen-specific T regulatory 1 cells induced in the respiratory tract by a bacterial molecule that stimulatesinterleukin 10 production by dendritic cells: a novel strategyfor evasion of protective T helper type 1 responses byBordetella pertussis. McGuirk P, McCann C, Mills KH:J Exp Med 2002, 195:221-231.Significance: Several subsets of T cells with regulatory function have been described in the past few years. However, verylittle was known about the induction of regulatory T cells in vivo,the antigens that these cells recognize or the factors that control their differentiation from naive T cells. This study is thefirst to show that a pathogen — Bordetella pertussis — evadesthe immune system by promoting the differentiation ofpathogen-specific regulatory T cells that are capable of inhibiting the development of a protective Th1 response.Findings: In this paper, the authors found IL-10-secreting CD4+

T cells in the respiratory tract of mice infected with B. pertussis.These cells were capable of inhibiting B. pertussis-specificIFN-γ production both in vitro and in vivo. Further experimentsshowed that the induction of these IL-10-secreting regulatoryT cells was dependent on the expression of filamentous hemagglutinin (FHA), a protein from B. pertussis that inhibitedIL-12 and stimulated IL-10 production by dendritic cells.

• IL-4-secreting CD4+ T cells are crucial to the developmentof CD8+ T-cell responses against malaria liver stages.Carvalho LH, Sano Gi G, Hafalla JC, Morrot A, de Lafaille MA,Zavala F: Nat Med 2002, 8:166-170.Significance: Although the development of strong CD8+ T cellresponses against infectious pathogens is often dependent onCD4+ T cells, the mechanisms by which these cells interact isnot clear. Here, the authors show for the first time that thesecretion of IL-4 by CD4+ T cells is one of the critical parametersinvolved in the cross-talk between CD4+ and CD8+ T cells.Findings: Immunization of mice with Plasmodium yoeliisporozoites induced the development of IFN-γ-secreting CD8+

T cells, which reacted to a peptide derived from the circum-sporozoite (CS) protein. Using mice that had been adoptivelytransferred with CS-specific TCR transgenic CD8+ T cells, theauthors showed that depletion of CD4+ T cells caused a

Paper alert 281

Immunity to infection

dramatic reduction in the number of CS-specific CD8+ T cellsthat were found in the spleen of infected animals six days afterinfection. Similar results were obtained when TCR transgenicT cells were adoptively transferred into IL-4- or STAT-6-deficientmice, further suggesting that CD4+ T cells promoted the development of CD8+ T cells by secreting IL-4.

• An immune evasion mechanism for spirochetal persistencein lyme borreliosis. Liang FT, Jacobs MB, Bowers LC,Philipp MT: J Exp Med 2002, 195:415-422.Significance: Several pathogens, such as Borrelia burgdorferi,can chronically infect their mammalian host despite the devel-opment of a strong antibody response directed against surfaceantigens. Although antigenic variation is one of the mechanismsused by this pathogen to evade this immune response, theauthors of this study showed that B. burgdorferi is also able todownregulate the expression of surface antigens that otherwisewould be targeted by bactericidal antibodies. Thus, regulationof gene expression, perhaps in response to tissue micro-environments, is one of the mechanisms by which pathogenscan evade the immune response.Findings: Infection of immunocompetent mice with B. burgdorferispirochetes induces a strong antibody response against outersurface protein (Osp) C. Here, the authors show that spirochetes that did not express OspC were selected in vivoconcomitantly with the appearance of anti-OspC antibodies.This phenomenon did not occur in severe combined immuno-deficient (SCID) mice but was restored when these animalswere injected with anti-OspC monoclonal antibody.

• Natural killer T cell ligand αα-galactosylceramide enhancesprotective immunity induced by malaria vaccines.Gonzalez-Aseguinolaza G, Van Kaer L, Bergmann CC,Wilson JM, Schmieg J, Kronenberg M, Nakayama T, Taniguchi M,Koezuka Y, Tsuji M: J Exp Med 2002, 195:617-624.Significance: NKT cells belong to a subset of lymphocytes thatrapidly secrete large amounts of IFN-γ and IL-4 upon in vivoactivation by α-galactosylceramide (αGalCer), a glycolipid orig-inally purified from marine sponges. Although the administrationof αGalCer to mice was previously shown to increase T cellresponses directed to various antigens, this is the first time thatsuch a treatment was shown to promote the development ofprotective immunity against an infectious pathogen. BecauseαGalCer can also stimulate human NKT cells, such a discoverymay be important for the development of new vaccines againsthuman pathogens.Findings: Parasitemia and liver stage parasites are readilyobserved in mice infected with live P. yoelii sporozoites.Here, the authors show that coinjection of αGalCer with asuboptimal dose of irradiated P. yoelii sporozoites inducedprotective immunity, whereas neither αGalCer nor irradiatedsporozoites alone were able to do so. αGalCer increased thenumber of IFN-γ-secreting CD8+ T cells that were specificfor the CS protein and prolonged the duration of theresponse. Further experiments showed that the adjuvantactivity of αGalCer required CD1d molecules, Vα14 NKTcells and IFN-γ.

•• Rapid cytotoxic T lymphocyte activation occurs in thedraining lymph nodes after cutaneous herpes simplex virusinfection as a result of early antigen presentation and notthe presence of virus. Mueller SN, Jones CM, Smith CM,Heath WR, Carbone FR: J Exp Med 2002, 195:651-656.

•• Visualizing priming of virus-specific CD8+ T cells byinfected dendritic cells in vivo. Norbury CC, Malide D,Gibbs JS, Bennink JR, Yewdell JW: Nat Immunol 2002,4:265-271.Significance: Although most viruses induce strong cytotoxicT cell responses, it remained to be determined which cells pre-sent viral antigens, and where and when presentation occurs.In these two studies, the authors show that virus-specific CD8+

T cells were activated in the lymph nodes (LNs) which drain thesite of infection as early as six hours after injection of either vaccinia or herpes simplex virus type 1 (HSV-1). Furthermore,Norbury et al. found that virus-infected antigen-presenting cellswere cleared very rapidly from the LNs. This latter result may berelevant for the development of viral vectors aimed at inducingand maintaining strong CD8+ T cell activation.Findings: Mueller et al. injected C57BL/6 mice with TCR trans-genic CD8+ T cells that were specific for the immunodominantepitope of the HSV-1 glycoprotein B. When these mice wereinfected with HSV-1, T cell activation occurred six hours later.Further experiments showed that T cell activation required the de novo synthesis of viral antigens but not the presence of the virus in the draining LNs. In the other study, Norbury et al.infected C57BL/6 mice with a recombinant vaccinia virus thatexpressed the enhanced green fluorescent protein (EGFP)linked to an ovalbumin (OVA)-derived peptide. Although virus-infected macrophages and dendritic cells (DCs) were readilydetected in the local draining LNs as early as six hours afterinfection, direct visualization of T-cell–DC interactions by confocal microscopy showed that only the DCs were capableof priming naïve virus-specific CD8+ T cells. Presentation eventually declined in parallel with the number of infected DCspresent in the LNs.

Selected by Anna VyakarnamKing’s College London, London, UK


• CTLA-4 upregulation during HIV infection: associationwith anergy and possible target for therapeutic intervention.Leng Q, Bentwich Z, Magen E, Kalinkovich A, Borkow G: AIDS2002, 16:519-529.Significance: This paper provides evidence for a role forcytotoxic T lymphocyte associated antigen 4 (CTLA-4) inHIV-1 pathogenesis.Findings: Engagement of CTLA-4 with B7 on antigen-presentingcells can interfere with CD28-induced T cell activation via B7, resulting in the termination of proliferation and in the induction of apoptosis of activated T cells. CTLA-4 is transientlyexpressed during normal T cell activation. The authors measuredintracellular pools of CTLA-4 by flow cytometry. CTLA-4 expres-sion was significantly higher in HIV patients compared withcontrols and correlated inversely with CD4 count. The cells that expressed CTLA-4 were shown to be activated CD3+

memory T cells that expressed HLA-DR. Compared with theCTLA-4–CD4+ compartment, CTLA-4+CD4+ T cells expressedhigher levels of CCR5, making them more susceptible to HIVinfection; they expressed lower levels of CD28 and CD4, makingtheir threshold for activation higher; and they expressed higherlevels of Ki-67, a marker of dividing cells that have been arrestedin G1. Conversely, the proliferative capacity of CTLA-4+CD4+

T cells to stimulation with anti-CD3 antibody or HIV antigens was lower than the CTLA-4– counterpart. The upregulation ofCTLA-4, which plays a key role in CD4+ and CD8+ T cell home-ostasis, could be central in HIV-1 induced anergy and apoptosis.

282 Paper alert

• Magnitude of functional CD8+ T-cell responses to the gagprotein of human immunodeficiency virus type 1 correlatesinversely with viral load in plasma. Edwards BH, Bansal A,Sabbaj S, Bakari J, Mulligan MJ, Goepfert PA: J Virol 2002,76:2298-2305.Significance: Although virus-specific CD8+ T cell responsesare likely to be important in the control of HIV-1 infection, fewstudies have shown a correlation between such responses andmarkers of disease progression. This study shows an inversecorrelation between the magnitude of the CD8+ T cell responseto HIV-1 Gag protein and virus load.Findings: The ELISPOT assay was used to measure the number of peripheral blood mononuclear cell (PBMC) IFN-γ+ cellsin that were specific for HIV-1 Gag, Pol, Nef or Env. Peptidepools spanning these proteins as well as recombinant Gag p24and gp160 proteins were used for stimulation. Twenty-sevenchronically infected HIV-1 patients were studied; the majority ofthese patients were off antiretroviral therapy. The magnitudeand breadth of the T cell response to the Gag peptide pool correlated inversely with virus load and directly with CD4+ cellcount by Spearmans rank correlation. The breadth of the subjects’ responses was defined as the number of peptide pools(10 peptides per pool) for which positive ELISPOT responseswere observed. CD4+ T cell counts correlated directly withresponses to Pol and integrase peptide pools but no correlationwith disease progression markers was noted with responses toeither Nef or Env peptides. Experiments performed on CD4+ orCD8+ fractions of PBMCs in a subset of patients showed that>70% of the response was lost in the fraction depleted ofCD8+ cells but not the fraction depleted of CD4+ cells. Theinability to observe similar strong correlation of CD8+ cellresponses with disease progression markers in previous effortsmay relate to several factors. For example, this study used alarge number of peptides to detect responses, thereby studyinga greater number of potential epitopes. In addition all patientshad detectable viral RNA despite being off antiviral therapy,emphasising the possible importance of continuous antigenstimulation for maintaining blood CD8+ T cell responses.Finally, there may be assay differences between various studies.In particular, the use of the intracytoplasmic staining assay usescostimulatory antibodies that may mask low responses. Thecorrelation of Gag responses with both CD4+ cell counts andvirus load reiterates the importance of specific CD8+ T cellresponses in immunity to HIV.

• Correlates of nontransmission in US women at high riskof human immunodeficiency virus type 1 infection throughsexual exposure. Skurnick JH, Palumbo P, De Vico A,Shacklette BL, Kamin-Lewis R, Mestecky J, Denny T, Lewis GK,Lloyd J, Praschunus R et al.: J Infect Dis 2002, 185:428-438.Significance: The development of anti-HIV vaccines is dependent on an understanding of the mechanisms of protectiveimmunity to HIV. This paper has characterised several aspects ofthe immune response in a cohort of US women who remaineduninfected despite multiple high-risk exposures to HIV.Findings: Seventeen women, who were uninfected despitemultiple exposures to HIV-1, and their partners were studied.CD8+ cell activity was noted to be a dominant factor in transmission. The majority of women had noncytotoxic CD8+

cell HIV-1 suppressive activity and CD8+ cells that producedmacrophage inflammatory protein 1β ( MIP1β). In additionthese women had strong CD4+ cell proliferative responses toHIV antigens and HIV-specific IFN-γ+ cells in PBMCs. Other

possible correlates of protection were, however, absent. Thewomen did not show increased cellular resistance to HIV-1infection; the majority were negative for neutralising anti-HIVantibody and lacked mucosal HIV-specific IgA. Interestingly, theimmune response of the non-transmitting HIV-1 infected partnerwas also noted to be a governing factor in nontransmission. Of the eight infected partners studied, all showed high CD8+

cell counts and produced CD8+ cell noncytotoxic HIV-1 suppression factor(s). These individuals also produced high levels of CD8+ cell MIP1β. Although this study did not characterise the nature of the noncytotoxic suppressor activityof CD8+ cells or dissect whether the HIV-specific responses ofIFN-γ+ cells in PBMCs reflected the presence of virus-specificIFN-γ+ CD4+ or CD8+ T cells, or both, the data neverthelessemphasise the importance of CD8+ cell noncytotoxic activityand MIP1β production as a correlate of HIV non-transmission.

• Induction of anti-human immunodeficiency virus type 1(HIV-1) CD8+ and CD4+ T-cell reactivity by dendritic cellsloaded with HIV-1 X4-infected apoptotic cells. Zhao XQ,Huang XL, Gupta P, Borowski L, Fan Z, Watkins SC,Thomas EK, Rinaldo CR: J Virol 2002, 76:3007-3014.Significance: The ability of dendritic cells (DCs) to induce anti-HIV-1 T cell responses in autologous PBMCs from HIV-1patients is shown. This may be an important mechanism of HIV-1immunogeniticity and provides a possible strategy for immunotherapyof HIV-1-infected patients on antiretroviral therapy.Findings: DCs were derived from CD14+ cells, enriched usingan immunomagnetic technique, from PBMCs of HIV-1-infectedindividuals. The CD14+ cells were cultured with granulocyte-monocyte colony-stimulating factor to obtain immature DCs(iDCs). Mature DC (mDCs) were obtained by treatment of iDCswith trimeric CD40L. HIV-1 antigen preparations were made byinfecting autologous anti-CD3-stimulated CD8– PBMCs with theX4 strain HIV-1 IIIB. To inactivate them and induce apoptosis,infected cells were treated with psoralen and UV irradiation. Toinduce necrosis, infected cells were freeze-thawed several times.The uptake by iDCs and mDCs of the necrotic and apoptotic cellpreparations was measured by flow cytometry, by staining withthe membrane flurochrome PKH 26 and correlating this withHLA-DR, which was shown to be markedly induced in iDCs andmDCs loaded particularly with the apoptotic cell preparation. Thecapacity of the DCs loaded with apoptotic and necrotic cells toinduce IFN-γproduction in autologous T cells was next measuredby ELISPOT. Significant induction of IFN-γ+ T cells was notedwhen mDCs were loaded with infected, apoptotic CD8– cellpreparations compared with uninfected apoptotic control preparations. mDCs loaded with necrotic-cell preparations failedto induce substantial IFN-γ production in autologous cells. Thisapproach may be particularly useful in enhancing T cell immunityto endogenous HIV-1 in an infected individual.

Selected by Jean-Laurent CasanovaLaboratory of Human Genetics of Infectious Disease, Necker-Enfants

Malades Medical School, Paris, Francee-mail: [email protected]

• Mutant chromatin remodelling protein SMARCAL1 causes Schimke immuno-osseous dysplasia. Boerkoel CF,Takashima H, John J, Yan J, Stankiewicz P, Rosenbarker L,

Paper alert 283

Immunogenetics

André JL, Bogdanovic R, Burguet A, Cockfield S et al.:Nat Genet 2002, 30:215-220.Significance: This paper reports on the first identification of a molecular basis for the Schimke T-cell immunodeficiency syndrome.Findings: Schimke immuno-osseous dysplasia (SIOD) is a rareautosomal-recessive multi-system syndrome of childhood.Children generally present with the triad of growth failure fromspondyloepiphyseal dysplasia, renal failure from glomerulosclero-sis, and autoimmunity and infections from T-cell immunodeficiency.Other clinical features include hypothyroidism, cerebral vasculitis,and bone marrow failure. The T-cell immunodeficiency consists ofa CD4+ cell lymphopenia with reduced T-cell proliferation to mito-gens. Homozygosity mapping of the SIOD locus on 2q35 led tothe identification of SMARCAL1 as a first disease-causing gene.The gene encodes a member of the SNF-2 family of proteins,which mediate DNA-nucleosome restructuring and participate in chromatin remodeling. Affected patients were found to behomozygous or compound-heterozygous for mis-sense, non-sense, frameshift or splicing mutations. Mis-sense mutationsaffected conserved residues in the SNF-2 domain. Foundereffects and a genotype–phenotype correlation were suggested bycomparing the epidemiological and clinical features of kindredswith SMARCAL1 mutations. From an immunological standpoint,this experiment of nature shows that the SNF-2-related SMAR-CAL1 protein is essential for the development and function ofT cells. It raises the question of which genetic processes are regulated by SMARCAL1 in T-cell progenitors and mature T cells.

Selected by Yang LiuOhio State University, Columbus, OH, USA


•• Generation of an LFA-1 antagonist by the transfer of theICAM-1 immunoregulatory epitope to a small molecule.Gadek TR, Burdick DJ, McDowell RS, Stanley MS, Marsters JCJr, Paris KJ, Oare DA, Reynolds ME, Ladner C, Zioncheck KAet al.: Science 2002, 295:1086-1089.Significance: This is a successful reduction of a nonlinear discontinuous but contiguous protein epitope from a protein toa small molecule on the basis of a rational and structurallydirected hypothesis. The small compound is more potent thancyclosporin A with regards to its ability to inhibit in vitro mixed-lymphocyte reactions.Findings: First, a small molecule designed on the basis of thestructure of the ICAM-1–LFA-1 binding site inhibits the interaction at an IC50 of 1.4 nM. Second, the small moleculesuppresses mixed-lymphocyte reactions at an IC50 of about3 nM. Third, the small molecule also inhibited delayed-type hypersensitivity in vivo.

• Natural killer T cell ligand alpha-galactosylceramideenhances protective immunity induced by malaria vaccines.Gonzalez-Aseguinolaza G, Van Kaer L, Bergmann CC,Wilson JM, Schmieg J, Kronenberg M, Nakayama T, Taniguchi M,Koezuka Y, Tsuji M: J Exp Med 2002, 195:617-624.Significance: The authors showed that innate immunityelicited by an NKT-cell ligand can be explored to enhance specific T-cell immunity.Findings: The NKT ligand α-galactosylceramide can be usedas an adjuvant to enhance T-cell-mediated protective immunity

against malaria. Its adjuvant activity can be attributed toenhanced CD8+ and CD4+ T cell responses and depends onactivation of Vα14+ NKT cells and CD1 molecules.

• Homeostatic T cell proliferation in a T cell-dendritic cellcoculture system. Ge Q, Palliser D, Eisen HN, Chen J:Proc Natl Acad Sci USA 2002, 99:2983-2988.Significance: The authors established an elegant in vitromodel to investigate homeostatic T-cell proliferation and thefunction of regulatory T cells. This model is valuable for investigating the elusive mechanism of the homeostatic T-cellproliferation in lymphopenic hosts.Findings: Co-culture of T cells, expressing a single TCR, withsyngeneic dendritic cells results in significant antigen-indepen-dent proliferation of T cells. This proliferation requirespresentation of peptide by self-MHC on dendritic cells as wellas soluble factors including IL-15, and is inhibited by contactwith CD25+CD4+ regulatory T cells.

Selected by Hugh Auchincloss Jr*, Gerry Waneck and Christian LeGuernMassachusetts General Hospital, Boston, MA, USA

*e-mail: [email protected]

• Regulatory T cells overexpress a subset of Th2 gene transcripts. Zelinka D, Adams E, Humm S, Graca L, Thompson S,Cobbold SP, Waldmann H: J Immunol 2002, 168:1069-1079.Significance: Many groups are beginning to analyze geneexpression in the regulatory T cells that appear to participate intransplantation tolerance. These studies have identified newmolecules, such as GITR (glucocorticoid-induced TNF receptor; also known as TNF receptor superfamily member 18[TNFRSF18]), that may be important in the function of theseregulatory cells.Findings: The authors analyzed differential gene expression ina variety of T cell populations including those from tolerant compared with rejecting skin grafts. They found that severalgenes showed increased expression in T cells from tolerantgrafts and in CD4+CD25+ T cells in normal mice, including prepro-enkephalin, GM2 ganglioside activator protein, GITRand integrin αEβ7. These genes represent a subset of thoseexpressed by Th2 cells.

• Stimulation of CD25++CD4++ regulatory T cells throughGITR breaks immunological self-tolerance. Shimizu J,Yamazaki S, Takahashi T, Ishida Y, Sakaguchi S: Nat Immunol2002, 3:135-142.Significance: The CD4+CD25+ population appears to be important in transplantation regulation as well as in the regulationof autoimmunity. Although GITR does not define the regulatory population, the effect of an antibody against it does provide newinsight into the mechanisms by which this population functions.Findings: The authors studied the effect of an antibody againstGITR. This molecule is predominately expressed onCD4+CD25+ T cells. The antibody appears to break the suppressive effect of CD4+CD25+ regulatory cells and toinduce an autoimmune disease in otherwise normal recipients.

• Preimplantation-stage stem cells induce long-term allogeneic graft acceptance without supplementary hostconditioning. Fandrich F, Lin X, Chai GX, Schulze M,

284 Paper alert

Immunotherapy

Transplantation

Ganten D, Bader M, Holle J, Huang D-S, Parwaresch R,Zavazava N, Binas B: Nat Med 2002, 8:171-178.Significance: The data provide suggestive evidence that allogeneic stem cells might be able to survive without immuno-suppression. However, it is also possible that the protocol usedwas another example of a donor-specific transfusion approachin which the heart transplant, after the portal infusion of donorantigen, allowed the prolonged survival of the stem cells. Theseresults need to be further explored in other models.Findings: This article provides evidence indicating the ‘preimplantation-stage stem cells’ (which the authors describeas ‘embryonic stem cell-like cells’) can be infused into the portalvein of rats and survive long-term without immunosuppression ifan allogeneic heart transplant from the same donor is performedseven days later. The presence of a recipient host thymusappeared to be necessary for the success of this protocol.

• Immature and mature CD8αα++ dendritic cells prolong thesurvival of vascularized heart allografts. O’Connell PJ, Li W,Wang Z, Specht SM, Logar AJ, Thomson AW: J Immunol2002, 168:143-154.Significance: In transplantation, donor dendritic cells (DCs) aretraditionally regarded as the main instigators of rejection althoughrecent studies have suggested that some immature donor DCsmay regulate T cell activation. This article provides evidence inmice that a single injection of allogeneic CD8a+ DCs — the principal thymic DC subset — resulted in the downmodulation ofanti-donor T cell responses and subsequent prolongation of heartgrafts. Important findings include the demonstration that bothmature and immature CD8a+ DCs regulate T cell functions, amechanism that does not involve immune deviation.Findings: As shown previously, both H-2b CD8a+ and CD8a–

DCs can prime naïve H-2k T cells in vitro for Th1 responses;this was confirmed here by the observation of strong prolifera-tion and Th1 cytokine synthesis. In contrast, only the CD8a+

DCs, given seven days before transplantation, significantly prolonged H-2b heart grafts in H-2k recipients. These recipientsalso showed impaired anti-donor T cell responses, which werenot reversed by the administration of IL-2. The elucidation of themechanisms of DC-mediated unresponsiveness will require further investigations although it appears that immune deviationis not the main pathway involved.

• CD25++CD4++ regulatory T cells prevent graft rejection:CTLA-4- and IL-10-dependent immunoregulation of allore-sponses. Kingsley CI, Karim M, Bushell AR, Wood KJ:J Immunol 2002, 168:1080-1086.Significance: The specificity of the control of CD4+CD25+

regulatory T cells (T-reg) over T cell activation has not yet beenestablished. This interesting study provides evidence that thedownmodulation of host T cell responses to heart allografts iscontrolled by donor-specific T-reg. The data also suggest that,in this model, T-reg-associated tolerance is essentially mediatedby CTLA-4 and IL-10.Findings: T-reg were first generated in CBA mice conditionedwith anti-CD4 antibodies and a blood transfusion from eitherB10 or Balb/c mice. The adoptive transfer of naïve CBA Th1cells (CD4+CD45RBhigh) together with T-reg (CD4+CD25+)that were primed against the donor (B10) led to acceptance ofB10 skin grafts whereas the injection of third-party (Balb/c)-primed T-reg had no effect. If treated with anti-IL-10-receptor oranti-CTLA-4 monoclonal antibodies at the time of adoptivetransfer, the recipients of B10 skin grafts rejected their

transplants, suggesting a potential role for these two moleculesin T-reg-mediated tolerance.

• Tolerization of dendritic cells by Ts cells: the crucial roleof inhibitory receptors ILT3 and ILT4. Chang CC,Ciubotariu R, Manavalan JS, Yuan J, Colovai AI, Piazza F,Lederman S, Colonna M, Cortesini R, Dalla-Favera R,Suciu-Foca N: Nat Immunol 2002, 3:237-243.Significance: These studies identify an important mechanismby which human CD8+CD28– T suppressor (Ts) cells mayinduce peripheral tolerance to specific HLA alloantigen.Findings: CD8+CD28– Ts cells purified from allospecific humanT cell lines (TCLs) inhibited the proliferative response of CD4+

cells isolated from the same TCLs. When immature APCs werepretreated with these Ts cells, they induced anergy in CD4+ Thcells. The anergizing APCs upregulated the ITIM-containinginhibitory receptors ILT3, whose ligand is unknown, and ILT4,which recognizes HLA class I. The Ts cells downregulatedexpression of costimulatory molecules on APCs and suppressed CD40–CD40L-mediated upregulation of CD80and CD86. Antibody blockade of both ILT3 and ILT4 wasrequired to reverse the inhibitory effect. NF-κB transcription inindicator cells was inhibited by constitutive expression of ILT3. Inheart allograft recipients experiencing no acute rejectionepisode in the first 6–8 months, CD8+CD28– cells induced theallospecific upregulation of ILT3 and/or ILT4 on donor APCs andsuppressed CD40–CD40L-mediated signaling. Cells frompatients that experienced rejection had no such effect.

Selected by Cezmi AkdisSwiss Institute of Allergy and Asthma Research, Davos, Switzerland


• ββ2 integrins are required for skin homing of primed T cellsbut not for priming naive T cells. Grabbe S, Varga G,Beissert S, Steinert M, Pendl G, Seeliger S, Bloch W, Peters T,Schwarz T, Sunderkötter C, Scharffetter-Kochanek K:J Clin Invest 2002, 109:183-192.Significance: β2 integrins are a group of heterodimeric molecules — including LFA-1, Mac-1 and p150,95 — which areinvolved in leukocyte adhesion and activation. They are composed of one CD18 molecule and one of the CD11 molecules: CD11a, -b, -c or -d. This study demonstrates a differential requirement for β2 integrins in CD18-deleted miceduring the two major compartments of skin inflammation,namely T cell extravasation and activation.Findings: In CD18-deleted mice T cell infiltration to allergiccontact dermatitis (ACD) and delayed-type hypersensitivity(DTH) lesions was strongly impaired, whereas migration ofLangerhans cell precursors and dendritic cells was normal. Incontrast, lymphatic organs of CD18-deleted mice containedspontaneously activated T cells with CD69, CD44high andCD62Llow expression. In addition, hapten-specific priming andactivation of naïve T cells was normal in the CD18-deletedmice, demonstrating that their T cell activation capacity is normal and that the defective ACD and DTH response are dueto an inability of T cells to extravasate into inflamed skin.

• Microarrayed allergen molecules: diagnostic gatekepersfor allergy treatment. Hiller R, Laffer S, Harwanegg C,

Paper alert 285

Allergy and hypersensitivity

Huber M, Schmidt WM, Twardosz A, Barletta B, Becker WM,Blaser K, Breiteneder H et al.: FASEB J 2002, 16:414-416.Significance: Currently, diagnosis of allergy is performed byserum specific-IgE determinations and provocation tests usingallergen extracts. This process does not identify the disease-elic-iting allergenic molecules but only defines allergen-containingsources. The authors have applied microarray technology todevelop a miniaturized allergy test containing ninety-four allergen molecules from the most common allergen sources.This technique allows the determination of IgE reactivity profilesof allergic patients with a single measurement.Findings: Seventy-eight recombinant and sixteen natural allergen molecules representing important allergen sourceswere microarrayed in triplicates onto glass slides and exposedto serum of allergic patients. IgE reactivity profiles determinedby microarray showed good correlation with skin-prick testsand dot-blots of allergen components on nitrocellulose.

• T cells and eosinophils cooperate in the induction ofbronchial epithelial cell apoptosis in asthma. Trautmann A,Schmid-Grendelmeier P, Krüger K, Crameri R, Akdis M, Akkaya A,Bröcker E-B, Blaser K, Akdis CA: J Allergy Clin Immunol 2002,109:329-337.Significance: Organ-specific homing of activated T cells andeosinophils, and effector functions in the lung representsequential immunological events in the pathogenesis ofasthma. Apoptosis of bronchial epithelial cells mediated byT cells and eosinophils represents the major tissue injury mech-anism leading to epithelial cell shedding in the asthmatic lung.Findings: Bronchial epithelial cells undergo cytokine-inducedcell death, showing morphological characteristics of apoptosismediated by activated T cells and eosinophils in asthma.T-cell-and eosinophil-induced epithelial cell apoptosis wasblocked by inhibition of IFN-γ and TNF-α, and caspase activa-tion. Other death receptors, such as DR3, DR4 and DR5, arenot expressed on bronchial epithelial cells. TNF-α upregulatesboth Fas and Fas-ligand as well as its own receptors, TNF-RIand II, on bronchial epithelial cells. Epithelial cells co-culturedwith activated-T-cell supernatants undergo apoptosis, demon-strating that cell-to-cell contact is not required for induction ofapoptosis. Eosinophils induce bronchial epithelial cell apopto-sis via the TNF pathway and necrosis by cytotoxic granulesubstances. Moderate-to-severe epithelial apoptosis wasdemonstrated to be relevant in vivo using bronchial biopsies ofasthmatic patients.

Selected by Allison GreenCambridge Institute for Medical Research, Addenbrooke’s Hospital,

Cambridge, UKe-mail: [email protected]

•• Arthritis critically dependent on innate immune systemplayers. Ji H, Ohmura K, Mahmood U, Lee DM, Hofhuis FMA,Boackle SA, Takahashi K, Holers VM, Walport M, Gerard Cet al.: Immunity 2002, 16:157-168.Significance: This report provides a strong link between FcγRsand the alternative pathway of complement activation with thedevelopment of arthritis.Findings: Transfer of serum from K/BxN arthritic mice cancause disease in healthy recipients. Using a series of FcγR-deficient

mice, the authors showed that efficient transfer of diseaserequired intact FcγRIII but not FcγRI or II. Similarly, using aseries of mice carrying null mutations for components of theclassical or alternative pathways of complement activation theyshowed that C5 was critical for arthritis development followingtransfer of K/BxN serum. By selective injection of serum intomice deficient in molecules located upstream of C5 the authorsidentified the alternative pathway leading to C5 activation fordisease precipitation. Finally, in vivo imaging techniques confirmed the importance of both FcγR and C5 in the initiationof arthritis by demonstrating that animals deficient in thesecomponents failed to develop infiltration of their joints by inflammatory cells.

•• Pancreatic lymph node-derived CD4++CD25++ regulatoryT cells: highly potent regulators of diabetes that requireTRANCE-RANK signals. Green EA, Choi Y, Flavell RA:Immunity 2002,16:183-191.Significance: This report demonstrates that the pancreaticlymph nodes (PLNs) and islets specifically propagate T regulatory(Treg) cells that control type 1 diabetes. Further, they describea new role for TRANCE–RANK interactions in the generation ofthese potent Treg cells.Findings: Restrictive expression of TNFα in the islets of B6 animals bearing B7-1 transgenically on their β-cells delays diabetes progression if TNFα is expressed from 0–25 days ofage. In contrast, expression of TNFα from 0–28 days of ageleads to rapid development of diabetes. FACS analysis of thetwo groups of mice demonstrated that repression of TNFα atday 25 increases CD4+CD25+ T (Treg) cell numbers 2–3-foldspecifically in the islets and PLNs (but not other lymph nodesor spleen) compared with animals that express TNFα from0–28 days. Adoptive transfer experiments demonstrated that2000 PLN-derived Treg cells from the former mice delayed disease progression in the latter mice. Up to 10 000 Treg cellsfrom other lymph nodes failed to protect recipient mice fromdisease progression. Selective ablation of TRANCE–RANKinteraction during the initiation of the regulatory phase resultedin decreased numbers of Treg cells in the PLNs and islets incomparison with isotype-control-treated mice. Histologicalstudies determined that this decrease in Treg cells resulted inincreased differentiation of islet-reactive CD8+ T cells intoCTLs and as a consequence rapid progression to diabetes.

•• Influence of a dominant cryptic epitope on autoimmuneT cell tolerance. Anderton SM, Viner NJ, Matharu P, Lowrey PA,Wraith DC: Nat Immunol 2002, 3:175-181.Significance: This paper highlights the importance of usingpeptides that correspond to naturally processed disease-linkedantigens, as opposed to cryptic peptides, as therapy towardsautoimmune diseases. Failure to use naturally processed peptides can prevent the induction of protective immunity toautoimmune disease.Findings: The authors generated a series of T cell lines following immunization of mice with MBP(89–111), which failsto generate protective immunity to EAE. Selective stimulation ofindividual lines with overlapping peptides with this sequenceindicated the presence of three distinct epitopes. Of thesethree, MBP(92–98)-specific T cells failed to respond to anynaturally processed MBP peptides, suggesting that the epitopewas cryptic. Both in vitro and in vivo investigations demonstrated that stimulation with MBP(89–101) selectivelyenhances the development of T cells that respond to cryptic

286 Paper alert

Autoimmunity

epitopes but will not respond to naturally processed MBP peptides. In vivo, T cells responsive to cryptic epitopes withinMBP(89–101) could not induce EAE whereas T cells responsive to naturally processed MBP peptides did. Further,administration of MBP(89–101) in tolerogenic form failed toelicit protective immunity to EAE, whereas tolerogenic adminis-tration of naturally processed MBP peptides resulted inprotective immunity.

• Tolerance to islet antigens and prevention from diabetesinduced by limited apoptosis of pancreatic ββ cells.Hugues S, Mougneau E, Ferlin W, Jeske D, Hofman P,Homann D, Beadoin L, Schrike C, von Herrath M, Lehuen A,Glaichenhaus N: Immunity 2002, 16:169-181.Significance: This paper provides evidence that early apoptosisof β-cells in NOD mice can result in the generation of regulatory cells following presentation of the apoptotic fragments by immature dendritic cells (DCs) in the PLNs, leading to protection against diabetes. These data promote thepossibility of using apoptotic β-cells to induce regulatoryresponses in pre-diabetic individuals.

Findings: Low dose injections of streptozotocin (SZ) inducedapoptosis of NOD β-cells within three hours and resulted in amore penetrative form of insulitis than seen in PBS (control)-treated mice. However, SZ-treated mice developed diseasewith decreased kinetics and penetrance compared with control mice. Adoptive transfer experiments showed thatsplenocytes from SZ-treated mice were poor at transferringdisease into NOD-SCID recipients in comparison withsplenocytes from PBS-treated mice. This lack of diseasetransfer was linked to the reduction in aggressive CD4+ Th1cell responses to islet antigen following SZ-treatment. Indeed,co-transfer of splenocytes from SZ-treated mice with diabetogenic splenocytes resulted in disease inhibition inRAG2–/–.NOD mice, whereas co-transfer of splenocytes fromPBS-treated mice did not inhibit the diabetogenic cell potential. In vitro proliferation, and FACS experiments usingindependent populations of antigen-presenting cells (APCs)isolated from the PLNs of SZ- or PBS-treated mice suggested that immature CD11c+CD11b+ DCs presentedislet antigen to islet-specific T cells to generate regulatorycells after SZ-treatment.

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