Natural and antibody-dependent cellular cytotoxicity in chronic myeloid leukemia patients in remission

Non-adherent peripheral blood mononuclear cells (NA-PBMNC) from 67 chronic myeloid leukemia (CML) patients in the first and two subsequent remissions, and 23 normal healthy donors were tested for NK and ADCC activities in short term chromium release assays using K562 and antibody-coated chicken RBCs as respective targets. CML patients in remission exhibited significantly reduced NK cytotoxicity (16. 1-19.7%) compared to normal healthy donors (47.4%). Of the patients tested, 55% exhibited NK levels below the mean percent cytotoxicity--2SD (12.5%) of normal donors (low responders), while 45% exhibited NK cytotoxicity above the 12.5% level (normal responders). On the other hand, CML patients in remission showed ADCC activity comparable to that of normal healthy donors (53.3%) irrespective of whether they belonged to normal NK responder group (55.5-65.0% ADCC) or low NK responder group (39.4-48.3% ADCC). The low or normal NK responder status of CML patients was not found to be related to either progression on the disease, or the type of drug used to bring about remission, or to the period in remission at the time of testing. In-vitro treatment of effector lymphocytes with recombinant human IFN alpha resulted in augmented of NK activity in both low and normal NK responder patients. The IFN-augmented NK activity in low responder patients however remained below the normal levels.