Selective IgA deficiency: analysis of Ig production in vitro.

The cellular basis of the pathogenesis of selective IgA deficiency (SIgAD) was investigated by examining surface immunoglobulin (SmIg) and in vitro pokeweed mitogen (PWM)-stimulated immunoglobulin (Ig) synthesis and by assaying in combination the counterpart lymphocytes from individuals with SIgAD and healthy donors. Peripheral blood lymphocytes (PBL) from 14 individuals with SIgAD synthesized normal amounts of IgG and IgM but did not synthesize normal amounts of IgA. Functional defects of lymphocytes for IgA synthesis were classified into four types: (i) B-lymphocyte dysfunction, (ii) increased function of suppressor T lymphocytes (Ts), (iii) decreased function of helper T lymphocytes (Th), and (iv) B-lymphocyte dysfunction and increased Ts function. The cells bearing SmIgG, SmIgM, and SmIgD were demonstrated at normal percentage ratios in all cases by immunofluorescent staining. The cells bearing SmIgA were at normal percentage ratios in the cases of T-lymphocyte dysfunction, while in the cases of B-lymphocyte defect SmIgA-bearing cells were reduced.