Inhibition of human B lymphocyte differentiation by a stable metabolite of cyclophosphamide (ASTA Z 7557, INN mafosfamide).

We have evaluated the immunosuppressive effect of a new stable derivative of cyclophosphamide (ASTA Z 7557) on human lymphocyte immunoglobulin biosynthesis in vitro. When graded amounts of the drug are added to lymphocyte cultures stimulated with the helper T cell-dependent activator (PWM), a marked inhibition of B cell proliferation and differentiation occurs. Lymph node cells are particularly sensitive to the drug, while splenocytes are relatively resistant. The agent exerts only a minor effect on immunoglobulin synthesis triggered by a direct B cell stimulant (S. paratyphi bacteria).