B cell activation in multiple sclerosis.

A microtechnique was established for the study of the limited numbers of cells available in CSF. The method allowed for the determination of the number of immunoglobulin-secreting cells (IgSC) as well as the quantitation of immunoglobulin or specific antibody secreted into the culture medium. Dose-response curves and kinetic profiles for the IgSC responses induced by pokeweed mitogen (PWM), a polyclonal B cell activator, were similar for CSF cells (CSFC) and peripheral blood mononuclear cells (PBMC). When equal numbers of unstimulated CSFC and PBMC from patients with multiple sclerosis (MS) were cultured, both the number of IgSC and the amount of secreted IgG were significantly greater in CSFC cultures. The addition of PWM resulted in the differentiation of B cells among both CSFC and PBMC, as shown by an increase of both the number of IgSC and the amount of secreted IgG. Results with cultures of unstimulated cell suspensions from MS patients suggested that CSF cells from these patients may be activated in vivo. The addition of mitomycin-C treated autologous peripheral blood mononuclear cells (PBMCM) to cultures of small numbers of CSFC or PBMC resulted in an augmentation of the number of IgSC in both, whether or not they were stimulated with PWM, and also in an increased secretion of IgG into the culture supernatants. This culture system should prove useful in functional studies when limited numbers of cells are available.