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 (T) and follicular regulatory T (T) cells. However, the analysis of circulating T (cT) and T (cT) cells in the pathogenesis of SIgMD has not been explored. We observed lower percentage of cT cells in SIgMD patients than in control group. However, we did not observe any significant difference in the percentage of cT 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 cT cells in SIgMD patients with specific antibody deficiency than in SIgMD patients with normal specific antibody response. Our results suggest that cT cells and their subsets are preserved in SIgMD patients. However, the role of lower percentage of cT cells in the pathogenesis of this immunodeficiency is not clear.