Antibody-dependent haemolytic activity of human leukaemic cells

Antibody-dependent cellular cytotoxicity (ADCC) of human leukaemic blood cells against human RBC treated with IgG isoantibody was studied by the 51Cr-release method. ADCC in this particular system is a property of normal phagocytic cells of the monocytic and myeloid series while lymphocytes are inactive. Well differentiated leukaemic monocytes from patients with acute monocytic leukaemia were highly cytotoxic and engulfed opsonized RBC. Promyelocytic leukaemic cells from two patients with acute promyelocytic leukaemia were cytotoxic and phagocytic. Seven patients with low differentiated acute myeloblastic leukaemia had no cytotoxic or phagocytic blood cells. Leukaemic B cells from patients with chronic lymphocytic leukaemia or prolymphocytic leukaemia lacked cytotoxic and phagocytic properties. It is concluded that ADCC against isoantibody-treated human RBC may be a tool to distinguish between well and poorly differentiated leukaemic cells of the monocytic or myeloid series.