IgD+IgM- B Cells in Common Variable Immunodeficiency.

Common variable immunodeficiency (CVID) is the most frequent form of primary hypogammaglobulinemia in adults. In addition to recurrent infections and respiratory manifestations, CVID patients may present several non-infection complications such as autoimmune diseases. The mechanisms that lead to immune dysregulation in CVID are not completely understood. Given the role of IgD on naïve B cells in the maintenance of tolerance and secreted IgD in the respiratory mucosa, we evaluated the frequency of IgD+ naïve and IgD+ memory B cells in CVID patients. Here, no differences were observed in the percentages and proliferative responses of anergic IgD+IgM-CD27- B cells between CVID patients, with or without autoimmune disease, and the control group. Interestingly, in the compartment of memory B cells, the percentage of IgD+IgM- cells was higher only in CVID patients with allergic rhinitis/allergic asthma. Our results may indicate that anergic IgD+IgM-CD27- B cells may not be compromised in our CVID cohort. However, IgD+IgM- memory B cells may play a role in the immunopathogenesis of allergic rhinitis/allergic asthma in CVID patients. Further studies are needed to better understand the participation of IgD+IgM- memory B cells in the immunopathogenesis of allergic rhinitis/allergic asthma in CVID patients.

Phenotypic analysis of T follicular helper and T follicular regulatory cells in primary selective IgM deficiency.

Selective IgM deficiency (SIgMD) is a rare immunodeficiency characterized by serum IgM below two standard of mean, and normal IgG and IgA levels. Both in human and mice with selective IgM deficiency, germinal centers cells are decreased. The development of germinal center and humoral immunity are regulated in part by follicular helper T (TFH) and follicular regulatory T (TFR) cells. However, the analysis of circulating TFH (cTFH) and TFR (cTFR) cells in the pathogenesis of SIgMD has not been explored. We observed lower percentage of cTFR cells in SIgMD patients than in control group. However, we did not observe any significant difference in the percentage of cTFH cells and their subsets between both experimental groups. When data were analyzed according to specific antibody response to pneumococcal polysaccharide, we observed a higher percentage of cTFH cells in SIgMD patients with specific antibody deficiency than in SIgMD patients with normal specific antibody response. Our results suggest that cTFH cells and their subsets are preserved in SIgMD patients. However, the role of lower percentage of cTFR cells in the pathogenesis of this immunodeficiency is not clear.