Disorders of regulatory T cells in patients with selective IgA deficiency and its relationship to associated autoimmune phenomena.

In vitro lymphocyte function of 13 patients with selective IgA deficiency was studied. IgG, IgA and IgM secretion by pokeweed mitogen-stimulated peripheral blood lymphocytes from normal donors and IgA deficient patients was measured by an enzyme-linked immunosorbent assay. Addition of concanavalin A or hydrocortisone and co-cultures of B and T cell enriched populations from patients and normal donors, allowed us to investigate B cell Ig production and T cell regulatory abnormalities. IgA production by these patients' B cells was either absent or very low, as compared to their total Ig production, even in the presence of optimal T cell help. Several T cell immunoregulatory abnormalities were seen in different patients. A moderate increase in suppressor activity selective for IgA production was observed in some, but does not appear to play a major role in the pathogenesis of the IgA deficiency. In others, with associated autoimmune phenomena, a decrease in suppressor T cell function was found.