B-cell differentiation in multiple sclerosis and the effect of intravenous ACTH.

B-cell differentiation was studied in patients with MS and in age- and sex-matched controls, using a pokeweed mitogen (PWM)-stimulated in vitro culture system. Peripheral blood lymphocytes were obtained and separated into T-cell and non-T-cell fractions. Autologous and allogeneic combinations of T cells and B cells were cultured in the presence of pokeweed mitogen for 7 days. Numbers of plaque-forming cells (PFC) were measured at the end of the culture period. T cells from MS patients before and after a 10-day course of adrenocorticotropic hormone (ACTH) were able to cooperate fully in the generation of PWM-generated PFC. B cells from MS patients showed a decreased ability to differentiate into PFC in the presence of either autologous or allogeneic T cells. No significant change in differentiation was observed after a 10-day course of intravenous ACTH. We were thus unable to demonstrate any alteration in T-cell function in MS but were able to demonstrate a decreased ability of MS B cells to differentiate into immunoglobulin-secreting cells. ACTH had no significant effect on these abnormalities.