T lymphocyte anergy during acute infectious mononucleosis is ...
Elevation of soluble CD23 in sera from patients with infectious mononucleosis
Transcript of Elevation of soluble CD23 in sera from patients with infectious mononucleosis
to estimate serum sCD23 levels. ELISA was performedaccording to the manufacturer’s instruction and as de-scribed elsewhere [Hashimoto et al., 1995]. Briefly,H107 was purchased from Nichirei Co. Ltd. (Tokyo,Japan) and E70 was purified from the ascites ofBALB/c mice injected intraperitoneally with hybrid-oma producing monoclonal antibody to sCD23 by a Pro-tein A immobilized agarose chromatography. AnELISA plate (Immunolon 4 flat bottom, DynatechLaboratories, Alexandria, VA) was coated with E70.Nonspecific binding was blocked with 10 mM PBS (pH7.2) containing 1% BSA and 0.05% Tween 20. sCD23standards and samples which had been diluted with 20mM Tris buffer (pH 7.5) containing 150 mM NaCl and10% normal calf serum were applied in duplicate andincubated at 37°C for 2 hr. After incubation, the platewas washed with PBS and incubated with alkalinephosphotase-conjugated H107 at 37°C for 2 hr. The en-zyme reaction was developed by addition of enzymesubstrate solution (3.33 mg/ml p-nitrophenylphosphatesolution dissolved in 1 mM diethannolamine (pH 10)containing 0.5 mM MgCl2. After incubation at 37°C for2 hr, color development was stopped by adding a stop-per solution (0.2 N NaOH) and absorbance at 405 nmwas measured in an ELISA reader. Statistical signifi-cance was analyzed using Mann-Whitney U-test. P val-ues less than 0.05 were considered significant.
RESULTS
Sera from patients with IM at the time of diagnosis(within 30 days after onset of disease) contained moresCD23 (n 4 16; range 1.16 to 8.36 ng/ml; mean ± SD3.20 ± 1.88; median 3.30) than sera from normal sub-jects (n 4 54; range 0.17 to 3.28; mean ± SD 1.33 ±0.70; median 1.22) (P < 0.01); Fig. 1. Multiple serumsamples were collected from five patients with IM toevaluate the changes in serum sCD23 levels relative tothe course of this disease. Figure 2 shows serialchanges in the levels of serum sCD23. Serum sCD23levels were elevated at time of diagnosis and they de-creased to the normal levels during the convalescentphase defined by the improvement of symptoms of IM.Relationship between serum sCD23 levels and clinicalfeatures of IM is shown in Table I In the six patientswho had lower serum sCD23 levels than the mean plus2SD of serum sCD23 levels in normal subjects, three(50%) and three (50%) had splenomegaly and lymph-adenopathy, respectively. On the other hand, in the 10patients who had higher serum sCD23 levels, nine(90%) and nine (90%) had splenomegaly and lymphade-nopathy, respectively. These results indicated that thepatients who had lower serum sCD23 levels than themean plus 2SD of serum sCD23 levels in normal sub-jects had a milder disease.
We also measured serum sCD23 levels in other viralinfections such as rubella and measles. Serum sCD23levels in four patients with rubella with mean age of18.8 years and in three patients with measles withmean age with 18.3 years were 1.18 ± 0.18 and 1.37 ±0.21 ng/ml, respectively.
DISCUSSION
sCD23 has been shown to be a regulatory molecule inimmune responses and exerts various activities eitheralone or synergistically with cytokines, such as the pro-motion of B cell and T cell growth [Caris et al., 1990;Gordon et al., 1991; Lecron et al., 1991]. In addition,this molecule has growth factor-like activities on EBV-transformed B cells [Conrad, 1990; Yodoi et al., 1989].The present results suggest that the elevated sCD23may play a role in an intense T and B cell proliferationin IM, including activation of B cells which are notinfected by EBV and could be the source of autoanti-bodies. A similar mechanism may account for the pos-sible association of EBV with autoimmune diseasessuch as Sjogren’s syndrome and rheumatoid arthritis,in which active EBV infection has been postulated[Saito et al., 1989; Takei et al., 1997]. Besides thesestimulatory activities of sCD23 on lymphocytes, onecould postulated that sCD23 may have a function toinhibit the infection of B cells by EBV. It has beenshown that CD21, the receptor for EBV, is capable ofbinding sCD23 [Auby et al., 1992]. sCD23 released intoserum of IM patients during acute phase of this disease
Fig. 1. Serum sCD23 levels in patients with IM and normal sub-jects. The horizontal short lines represent the mean of each group andthe dashed line represents the mean plus 2SD of normal subjects.
Soluble CD23 in Infectious Mononucleosis 385