Antibody-dependent monocyte-mediated cytotoxicity. Serial studies in acute myeloid leukaemia.

Antibody-dependent cytotoxicity mediated by purified monocytes was determined in 42 patients suffering from acute myeloid leukaemia (AML). Compared to 9 patients with acute bacterial infection and to 42 normal controls, patients with untreated AML exhibited deeply depressed monocyte cytotoxicity. Cytotoxicity was reduced in each of the cytomorphological subgroups of AML. Patients attaining remission showed the same cytotoxicity as patients not attaining remission. During remission monocyte cytotoxicity increased significantly, but normal function was not achieved. Patients receiving chemotherapy alone exhibited the same defective cytotoxicity as patients receiving chemotherapy plus immunotherapy with Corynebacterium parvum. The termination of maintenance chemotherapy after remission for 1 year did not normalize cytotoxicity. Also the cytotoxicity of normal monocytes was not affected by patient serum. It is suggested that the reduced monocyte cytotoxicity observed in AML is related to the leukaemic process. The lack of complete normalization during the remission may indicate the continuous presence of an intrinsic defect of monocytopoiesis.