T- and B-cell functions in IgA-deficient patients.

In vitro lymphocyte function of 60 IgA-deficient patients (IgAdp) were studied. In the mitogen-induced lymphocyte activation test, peripheral blood mononuclear cells (PBMC) of IgAdp showed a weaker response to pokeweed mitogen (PWM) than those of controls (P less than 0.05), and the responses to phytohaemagglutinin (PHA) and concanavalin A (Con A) were normal. The amounts of IgA, IgG, and IgM secreted by PBMC from controls and IgAdp were measured in vitro by enzyme immunoassay. B cells were activated by PWM with or without hydrocortisone (HC) to inhibit HC-sensitive suppressor cells. Lymphocytes of IgA-deficient patients synthesized only minute amounts of IgA in vitro and the amounts of IgA synthesized correlated well with the serum IgA levels. Both IgG and IgM secretion by PWM-stimulated PBMC of IgAdp were also subnormal. The lymphocyte subset analysis in the peripheral blood revealed normal numbers and ratios of T cells, but IgAdp had reduced percentages of surface IgA-bearing cells. Co-culture experiments with isolated B cells, CD4- and CD8+ cells from IgAdp. and controls showed low B-cell capacity for IgA production as the most constant finding. Defects in T-cell functions or changes in the proportions of surface antigen-carrying lymphocytes (other than IgA-) were infrequent and were not associated with any particular group of patients or type of IgAd (primary, acquired, or transient).