SELECTIVE SUPPRESSION OF RESTING B-CELL FUNCTION IN PATIENTS WITH SYSTEMIC LUPUS-ERYTHEMATOSUS TREATED WITH CYCLOPHOSPHAMIDE

The immunological function of patients with inactive systemic lupus er ythematosus (SLE) receiving chronically administered, low-dose cycloph osphamide (CY) together with prednisolone (PSL) was compared with that of inactive patients receiving PSL alone. A striking selective suppre ssion of ''genuine'' resting, but not ''partially'' or ''fully'' activ ated, B cell function was noted in the patients receiving PSL + CY as measured by Staphylococcus aureus Cowan I (SAC)-induced proliferative responses by Percoll-separated small resting B cells of high density; the small resting B cells sedimenting in a high density fraction were more responsive to SAC in patients treated with PSL alone than those i n normal controls. However, the spontaneous proliferation and spontane ous secretion of immunoglobulins by peripheral blood B cells were elev ated in both the patient groups. The proliferative responses to phytoh aemagglutinin and concanavalin A by T cells were not significantly dif ferent between both patient groups. The data indicate that the genuine resting B cells may be the major target for the CY effect in SLE, and thus such selective suppression may help explain the efficacy of CY a nd PSL together in treating SLE.