Monoclonal antibody-defined B lymphocyte subpopulations in primary immunodeficiency disorders

Peripheral blood from 23 patients with common variable immunodeficiency (CVI) and 5 with selective IgA deficiency (SIAD) was examined for the proportions of B lymphocytes defined with monoclonal antibodies FMC 1 and FMC 7. In healthy controls, FMC 1 monoclonal antibody reacts with antigen present on almost all surface Ig+ B lymphocytes; FMC 7 monoclonal antibody reacts with antigen present only a subset of surface Ig+ and FMC 1+ B cells. In 13 of 23 patients with CVI and all patients with SIAD, a relative increase in FMC 7+ B cells, resulting in proportions of FMC 7+ B cell comparable to surface Ig+ or FMC 1+ B cells was observed. These data suggest abnormality of the proportion of B cell subsets in patients with CVI and SIAD that could suggest an intrinsic defect of B cells in these disorders.