Depressed in Vitro B—Lymphocyte Differentiation in Systemic Lupus Erythematosus

Abstract

Abstract Peripheral blood lymphocytes from 20 patients with systemic lupus erythematosus (SLE) and 21 normal donors were incubated with pokeweed mitogen in order to assess in vitro terminal—differentiation of B lymphocytes into cells synthesizing intracytoplasmic immunoglobulin (Ig). Although the percentage (mean ± SEM) of B lymphocytes bearing surface Ig in the initial cell suspensions was not statistically different in SLE than in normal subjects (15 ± 2.2% versus 16 ± 1.9%, respectively), the frequency of cells containing intracytoplasmic Ig per 10 3 mononuclear cells was significantly lower in mitogen—stimulated cultures derived from the patients than from the normal controls (10 ± 2.3 versus 56 ± 13.0 for IgM, P < 0.01; 21 ± 3.6 versus 63 ± 10.4 for IgG, P < 0.01; 13 ± 3.1 versus 24 ± 3.8 for IgA, P < 0.05 respectively). Coculturing active SLE lymphocytes with cells from normal subjects resulted in a significant ( P < 0.05) increase in the frequency of cells containing intracytoplasmic IgG when stimulated with pokeweed mitogen. Moreover, culturing SLE lymphocytes in cell—free media derived from activated normal lymphocytes also resulted in a significant increase in the frequency of IgG—containing cells. These results suggest that B—lymphocyte differentiation in vitro is depressed in SLE and may, at least partially, be reversed by products derived from normal lymphocytes.