Mitogen-induced plasma cell differentiation in patients with multiple sclerosis.

Cellular interactions involved in mitogen-stimulated plasma cell differentiation were investigated in eight patients with severe but stable multiple sclerosis (MS). No significant differences were detected between normals and MS patients with regard to percent of B lymphocytes and T lymphocytes in peripheral blood. Autologous and allogeneic combinations of normal and MS B and T cells were stimulated with pokeweed mitogen (PWM) and E. coli lipopolysaccharide (LPS), and plasma cell differentiation was monitored after 7 days in culture. T lymphocytes from patients with MS induced 2- to 4-fold increases in plasma cell development when combined with normal B cell fractions. Allogeneic combinations on normal B and T cells did not provide enhanced plasma cell generation. B lymphocytes from MS patients exhibited poor responses to both PWM and LPS when cultured with their own or normal T cells. Such B cell fractions did not differ from normals with regard to percent monocytes or surface Ig+ B lymphocytes initially contained in these cell populations. We conclude that T cells from MS patients are able to provide excessive help for normal B cell differentiation due either to increased T helper activity or deficient T suppressor activity. B cell differentiation may be diminished in MS patients as a result of a deficiency of a population of B cells in blood that are able to be stimulated by polyclonal B cell activators.