Peripheral blood lymphocytes or T and B cells from systemic lupus erythematosus (SLE) patients and normal individuals were stimulated with pokeweed mitogen and the intracytoplasmic immunoglobulin positive cells were observed. From the results of coculture of normal and SLE cells, it was postulated that SLE patients had not only a loss of suppressor T cell activity but abnormal B cell function. Further experiments showed that these abnormalities in SLE lymphocytes remained in spite of corticosteroid treatment or inactive disease.