Selective suppression of resting B cell function in patients with systemic lupus erythematosus treated with...

The immunological function of patients with inactive systemic lupus erythematosus (SLE) receiving chronically administered, low-dose cyclophosphamide (CY) together with prednisolone (PSL) was compared with that of inactive patients receiving PSL alone. A striking selective suppression of "genuine" resting, but not "partially" or "fully" activated, 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 in normal controls. However, the spontaneous proliferation and spontaneous secretion of immunoglobulins by peripheral blood B cells were elevated in both the patient groups. The proliferative responses to phytohaemagglutinin and concanavalin A by T cells were not significantly different 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 and PSL together in treating SLE.