Regulatory T Cells and HIV Infection
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Regulatory T Cells and HIV Infection
ผศ. ศักด์ิชยั เดชตรยัรตัน์ดร. พานทอง สงิหบุ์ตรา
หอ้งปฏิบติัการเอชไอวี แขนงวชิาภมูคิุ้มกัน วทิยาคลินิก
คณะเทคนิคการแพทย์ มหาวยิาลัยเชยีงใหม่
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Immune Responses
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Adaptive Immune Response
How this is achieved?
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Self-ToleranceThe immune system discriminates between self and non-selfEstablishing and maintaining unresponsiveness to self
Central Tolerance (clonal deletion)Occurs within central lymphoid organsBefore lymphocytes mature
Peripheral ToleranceOccurs in peripheral lymphoid organsAfter lymphocyte mature
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Proposed Mechanisms of Peripheral Tolerance
Rendered anergic or further deleted if encounter self-antigen in the peripheryFail to be activated because of low avidities to self-antigensLack of co-stimulation from APCsSecluded from target self-antigensRegulatory T cells actively down-regulate the activation and expansion of self-reactive lymphocytes
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Regulatory T Cells (Tregs)
“Suppressor cells” (Gershon et al. 1972) CD4+ T cells that express the IL-2 receptor α chain control autoreactive T cells in vivo (Sakaguchi et al. 1995) Antigen-specific T-cell clones suppressed the proliferation of CD4+ T cells in response to antigen and prevented colitis in a severe combined immunodeficiency mouse model (Groux et al., 1997)
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Regulatory T Cells (Tregs)
Identification of several types of Tregs“Regulatory T cells” is a preferred term
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Types of Tregs
Levi G., et al. Seminars in Immunology. 2011. in press.
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CD4+CD25+Foxp3+ Regulatory T Cells
Fundamental in controlling various immune responses Discovered by Sakaguchi et al. 5-10% of peripheral CD4+ T cells Expressed high level of IL-2Rα (CD25), Foxp3 Developed in thymus and present in healthy individuals from birth
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γδ Regulatory T Cells
Comprise 5% of total T cells in peripheral lymphoid tissues Enriched in skin, intestine and genito-urinary tract
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Natural Killer T Cells (NKT)
Produce large amount of Th1 (IFN-γ, TNF-α) and Th2 (IL-4, IL-10 and IL-13) cytokines Play roles in tumor rejection, resistance to pathogenic infection, autoimmune diseases and allograft acceptance
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Regulatory T Cells Type 1 (Tr1)
Arise in the periphery following activation of naïve T cells with Ag in the presence of IL-10 Produce
high IL-10, TGF-β and IL-5 low IL-2 and IFN-γ no IL-4
Do not express high levels of either CD25 or Foxp3
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T Helper 3 (Th3)
Induced in gut environment with high TGF-β, Th2 cytokines, subsets of DC and oral antigens Produces TGF-β Induces tolerance to nonpathogenic resident bacteria and food antigens
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CD8+ Regulatory T Cells
Arise either from thymus or in response to foreign or self antigens CD8+CD25+ share similar phenotypes and functions with CD4+CD25+ T cells Express increased mRNA levels of Foxp3, GITR, CCR8, TNFR-2 and CTLA-4 Following activation, express TGF-β1 and CTLA-4, do not produce cytokines
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Doble Negative T Cells (DN)
CD4-CD8-CD3+ comprised 1-2% of total CD3+ T cells in blood and lymph nodes Express a unique set of cell surface markers
TCRαβ, CD25, LFA-1, CD69, CD45, CD30, CD62L and CTLA-4
Produce High IFN-γ Low IL-10 and IL-4No IL-2
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Functions of Tregs
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HIV Infection
Loss of CD4+ T cells Chronic immune activation Progressive immune disfunction Impaired immune responses
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Possible Roles of Treg in HIV Infection
T cell
Quiescent
resistant to infection
T cell
Activated
establish infection
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Possible Roles of Treg in HIV Infection
Loss of Treg
destruction of T cellsdeterioration of immune function
T cell
Hyperactivation
Expand of TregExcessive Treg activity
No protective immune responsesEstablish carrier state of infection
T cell
Suppressed
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Changes in Treg Numbers in HIV DiseaseDisease
State Treg Phenotype Change Organ
No ART CD4+CD25+ - Peripheral blood
CD4+Foxp3+ Increase Lymph node
CD4+CD25+Foxp3+ - Peripheral blood
Increase Peripheral blood
Decrease Peripheral blood
Increase Mucosa
Increase Tonsils
Increase Lymph node
CD4+CD25hiCD62Lhi Decrease Peripheral blood
CD4+CD25+CD127lo Increase Peripheral blood
CD4+CD25+CD127lo45RO+ -/ Peripheral blood
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Changes in Treg Numbers in HIV Disease
Disease State Treg Phenotype Change Organ
On ART CD4+CD25+ Increase Peripheral blood- Peripheral blood
CD4+Foxp3+ Increase Lymph nodeSpleen
CD4+CD25+Foxp3+ - Mucosa- Mucosa
- Peripheral bloodTonsils
CD4+CD25+CD127lo Increase Peripheral blood
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Treg Function in HIV Infection
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How to Identify Tregs?
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What are these markers?
A single chain molecule on T-helper cellBinds to 2 domain of MHC-IIIncrease the sinsitivity of T cell to Ag
CD4
Interleukin-2 receptor α-chain (IL-2Rα) Receptor for IL-2, T-cell growth factor
CD25
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25
What are these markers?
Forkhead ⁄ winged-helix transcription factor box P3 Transcriptional repressor Most specific Treg marker currently Key factor in controlling Treg development
Foxp3
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What are these markers?
Cytotoxic T lymphocyte associated protein-4 Binds B7.1 (CD80)/B7.2 (CD86) Major negative regulator of T-cell responses
CTLA-4 (CD152)
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What are these markers?
Glucocorticoid-induced tumor necrosis factor receptor Required for the induction of apoptosis Expressed on various lymphocytes at different levels High surface expression of GITR is only confined to resting nTreg cells in the periphery and thymus
GIRT
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What are these markers?
Specific receptor chain for IL-7 IL-7 control thymopoiesis and homeostasis of peripheral T lymphocytes
IL-7Rα (CD127)
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%Cell Expressing Treg Markers
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Detection of nTregs
1. PBMC Isolation (Ficoll gradient centrifugation)
2. Cell surface staining (CD4 and/or CD25)
3. Intracellular staining (Foxp3)
4. Flow cytometric detection and analysis
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FACS profile of CD4+CD25+ Cells
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FACS profile of CD4+CD25+ Cells
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CD4
Foxp
3Foxp
3
CD4
Isotypes control
FACS profile of CD4+Foxp3+ Cells
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FACS profile of CD25+Foxp3+ Cells
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Challenges in Identification of Tregs
Current markers are not truely Treg-specific All T cells express CD25 upon activation CTLA-4 is upregulated on all CD4+ and CD8+ T cells, 2–3 days following activation GITR is induced in T cells upon activation CD127 is downregulated in most CD4+ T cells upon activation Most human CD4+ and CD8+ T cells transiently express Foxp3 upon activation
Isolation of Treg using Foxp3 is limited to only phenotypic study