In-vitro analysis of defective IgA production in selective IgA deficiency in childhood.

IgA production from B cells can be driven by three signals (anti-Ig antibody, B cell growth factor and helper T cell factor). It was thought that this three signal system might be a way other than the mitogen-stimulated system, to access B cell differentiation into Ig-producing cells. Seven children with IgA deficiency were investigated by this method. In all cases B cell differentiation was defective when using this three signal system. In one case, IgA producing cells were generated in normal number from B cells when stimulated with pokeweed mitogen in the presence of normal T cells. Definite abnormality of regulatory T cells in the IgA production was observed in only one case. These observations suggested that the main cause of IgA deficiency in most cases is the defect of B cells to differentiate into IgA secreting cells.