Increased expression of CD23 on peripheral blood B cells and macrophages/monocytes during acute infectious mononucleosis

Comparative immunophenotypic features of EBV-positive and EBV-negative atypical lymphocytosis

BACKGROUND

Atypical lymphocytosis is a common peripheral blood abnormality seen not only in Epstein-Barr virus (EBV)-associated acute infectious mononucleosis but also in other conditions, including other viral infections, cancer, immune reactions, etc. Despite numerous reports of individual immunophenotypic alterations in EBV-positive infectious mononucleosis, a detailed comparative analysis of the immunophenotypic changes of peripheral blood lymphocyte subsets in infectious mononucleosis and other forms of atypical lymphocytosis is lacking.

METHODS

Multiparametric flow immunocytometry with 26 monoclonal antibodies was performed on peripheral blood lymphocytes from 97 cases of atypical lymphocytosis and 37 normal controls. Atypical lymphocytosis was defined as absolute lymphocytosis with >10% atypical lymphocytes. Absolute or relative mean values of various lymphocyte subsets from EBV-positive cases, EBV-negative cases, and normal controls were compared with the Student's t-test.

RESULTS

Highly significant abnormalities detected in atypical lymphocytosis include increases in CD3+/CD8+, CD3-/CD16/56+, CD3+/gammadelta+, CD8+/CD48-, CD8+/CD57-, CD8+/CD95+, CD4+/CCR5+ CD4+/CD7-, CD4+/CD43-, CD4+/CD48-, and CD4+/CD62L- subsets. In contrast, no change in absolute CD4+ T cell and CD19+ B cell counts is seen. When compared with EBV-negative cases, EBV-positive cases are characterized by younger age, and increased numbers of absolute lymphocytes, atypical lymphocytes, CD8+ cells, NK cells, gammadelta T cells, CD8+/CD45RO+ cells, CD8+/CD57- cells, and CD8+/CD28+ cells.

CONCLUSIONS

All forms of atypical lymphocytosis are characterized by a marked increase in activated CD8-positive T cells, a moderate increase in NK cells, and no increase in CD4-positive T cells and B cells. Although morphologically indistinguishable, EBV-associated mononucleosis is characterized by several significant differences in peripheral blood lymphocyte subsets when compared with EBV-negative atypical lymphocytosis, most notably increased numbers of CD57-negative CD8 T cells and gammadelta T cells.

Increased expression of CD23 (Fc(epsilon) receptor II) by peripheral blood monocytes of aids patients

Monocytes expressing the Fcepsilon receptor II (CD23) play important roles in inflammatory and allergic immune responses. We found that peripheral blood monocytes of AIDS patients express increased levels of CD23, compared with monocytes of healthy HIV-1-seronegative individuals (controls) (p < 0.05). We compared expression of monocyte CD23 with expression of monocyte Fcgamma receptors (CD16, CD32, CD64), plasma/serum levels of IgE (also IgM, IgG, IgA), and Th1 (IFN-gamma) and Th2 (IL-4, IL-10) cytokines. We found that monocyte CD23 expression directly correlated with monocyte CD16 expression (p < 0.01, R = 0.58), which was also increased in AIDS patients; there was no correlation with CD32 or CD64 or with soluble factors in plasma/serum (i.e., IgE, IL-4, IL-10, and IFN-gamma). Interestingly, despite the known ability of IL-10 to downregulate monocyte CD23 expression, plasma IL-10 levels were increased in these AIDS patients compared with controls (p < 0.05). We thus evaluated the effect of AIDS and control plasma or rhIL-10 to regulate CD23 expression by monocytes in cultures (24 hr) of healthy human cells +/- treatment with anti-IL-10R blocking antibody. We found that anti-IL-10R blocking antibody treatment had no effect on monocyte CD23 expression in cultures containing AIDS plasma, but increased monocyte CD23 expression in cultures containing control plasma (p < 0.05) or rhIL-10. In conclusion, the identification of increased monocyte CD23 expression in AIDS patients may further characterize the aberrant activated phenotype of monocytes during the immunopathogenesis of HIV-1 disease. Further, monocyte CD23 expression does not appear to be suppressed by the IL-10-enriched environment in AIDS.

CD14+CD16+ monocyte subpopulation in Kawasaki disease

Kawasaki disease (KD) is an acute febrile illness caused by vasculitis, occurring in early childhood. We have demonstrated that the activation of monocytes/macrophages plays a central role during acute KD. Recently, it has been reported that the CD14+CD16+ monocyte subpopulation plays a more important role in inflammation. In this study, we investigated the peripheral blood CD14+CD16+ monocyte subpopulation by flow cytometry, and serum levels of IL-10 and IL-12 using a sandwich ELISA in 28 KD patients. We also investigated this subpopulation in patients with bacterial infections, mononucleosis and anaphylactoid purpura, since the cause of KD remains unknown. We observed an increase in the number of CD14+CD16+ monocytes with acute KD, which was a positive correlation with C-reactive protein levels, and we observed only the patients with severe bacterial infections had increased this subpopulation during the acute stage among control diseases. In addition, we found that the serum levels of IL-10, but not IL-12, were higher during acute KD. These data suggest that increased peripheral blood CD14+CD16+ monocytes are part of the regulatory system of monocyte function during acute KD.

An animal model for acute and persistent Epstein-Barr virus infection

Epstein-Barr virus (EBV) is a human lymphocryptovirus that causes infectious mononucleosis, persists asymptomatically for life in nearly all adults, and is associated with the development of B cell lymphomas and nasopharyngeal carcinomas. A highly similar rhesus lymphocryptovirus naturally endemic in rhesus monkeys was used to orally infect naïve animals from a pathogen-free colony. This animal model reproduced key aspects of human EBV infection, including oral transmission, atypical lymphocytosis, lymphadenopathy, activation of CD23(+) peripheral blood B cells, sustained serologic responses to lytic and latent EBV antigens, latent infection in the peripheral blood, and virus persistence in oropharyngeal secretions. This system may be useful for studying the pathogenesis, prevention, and treatment of EBV infection and associated oncogenesis.

Decreased levels of circulating IFN-alpha and increased sCD23 in patients with acute infectious mononucleosis

Epstein-Barr virus (EBV) is the etiological agent for acute infectious mononucleosis (AIM). It is also associated with certain malignant disorders in individuals with immunodeficiencies such as B cell lymphoproliferative disorder (BLPD). Our previous study with BLPD patients had demonstrated significantly higher serum IL-4 and IgE levels and significantly decreased IFN-alpha levels. These observations were consistent with the model of regulation of B cell growth by T cell-derived cytokines, in which IL-4 promotes B cell growth and switch to IgE synthesis whereas IFN-alpha and IFN-gamma inhibit these IL-4 mediated effects. Since AIM is also EBV associated, this study was designed to examine IL-4, IFN-alpha, IFN-gamma, IgE, and soluble CD23 (sCD23) serum levels in AIM patients. In this study we report for the first time that in contrast to BLPD patients, AIM patients did not exhibit increased levels of IL-4 and IgE; however AIM patients to exhibit decreased IFN-alpha levels and, additionally, also exhibit significantly higher sCD23 levels. This could result in B cell activation and have implications for the survival of the virus in B cells.

Soluble CD23 antigen in Kawasaki disease and other acute febrile illnesses

Kawasaki disease (KD) is an acute febrile illness of early childhood. Although the epidemiology of KD suggests an infectious agent, the cause still remains unknown. Intense immune activation during the acute disease has been well documented. Quantitative determination of soluble CD23 in serum can serve as an index of macrophage/monocyte or B-cell activation. To further characterize the immunological profile in KD, we investigated whether soluble CD23 levels in serum increase during the acute disease. In addition, we compared soluble CD23 levels in 33 patients with acute KD with levels in ten patients each with measles, rubella, infectious mononucleosis, and scarlet fever to determine if marked elevations in soluble CD23 were unique to acute KD. Patients with KD, rubella and infectious mononucleosis, but not patients with measles or scarlet fever, had increased soluble CD23 levels in serum during the acute stage, as compared to age-matched control subjects (P < 0.01). These data suggest infection with Epstein-Barr virus and rubella and acute KD are all characterized by B-cell and macrophage/monocyte activation.

Soluble CD23 in human immunodeficiency virus type 1 infected patients

The level of sCD23 produced in the course of human immunodeficiency virus (HIV) infection was measured in patients grouped according to the Centers for Disease Control by using an immunoradiometric assay. Soluble CD23 was evaluated in supernatants of peripheral blood mononuclear cell (PBMC) (10(6) cells/ml) stimulated by phytohemagglutinin (PHA). Compared with healthy controls (m +/- S.D. = 1.0 +/- 0.34 U/ml, n = 7), higher values were observed in some of the patients of group II (asymptomatic) (m +/- S.D. = 2 +/- 1.33, n = 9) and some of the patients of group IV (AIDS) (m +/- S.D. = 1.3 +/- 1.40, n = 8). Those results prompted us to compare the plasma levels of sCD23 in group II and group IV HIV-infected patients and in healthy individuals. Soluble CD23 plasma levels in healthy patients (n = 42) ranged from 0 to 1.5 U/ml (m +/- S.D. = 0.9 +/- 0.33), in group II patients (n = 17) from 0 to 3 U/ml (m +/- S.D. = 0.92 +/- 0.83) and in group IV patients (n = 73) from 0 to 2.9 U/ml (m +/- S.D. = 1.15 +/- 0.71). The differences between the patients and the healthy individuals were not statistically significant but individual sCD23 values higher than 2 U/ml were obtained in 6% of the group II patients and 16.7% of the group IV patients. Increased values of sCD23 were obtained in plasma from patients with secondary infectious diseases (groups IV-Cl and IV-C2) and from patients without secondary infectious diseases (group II, group IV-A and group IV-B).(ABSTRACT TRUNCATED AT 250 WORDS)

Soluble ICAM-1 levels in serum during acute infectious mononucleosis

Intercellular adhesion molecule-1 (ICAM-1) has been reported as a T-cell, B-cell or macrophage/monocyte activation antigen. We investigated whether soluble ICAM-1 levels in serum increased during the acute stage in 11 patients with infectious mononucleosis (IM). Serum ICAM-1 levels were measured by a double determinant immunoassay using 2 monoclonal antibodies in the FAST system. Serum ICAM-1 levels in patients with IM increased during the acute stage. There was a positive correlation between serum ICAM-1 levels and absolute counts of peripheral blood mononuclear cells. Our results suggest that the elevated serum ICAM-1 levels are based on the increased counts of activated peripheral blood mononuclear cells and that ICAM-1 is a part of the regulatory system of immune reactions during acute IM.