Immunologic evaluation of long-term effects of childhood ALL chemotherapy: analysis of in vitro NK- and K-cell activities of peripheral blood lymphocytes.

Twenty-five children with acute lymphoblastic leukemia (ALL) were tested for natural killer (NK) and K-cell activity in vitro using the nonsensitized myeloid/erythroid cell line K562 and the K562 sensitized with rabbit antithymocyte globulin, respectively. The patients consisted of two groups: 1) 13 patients in continuous first remission undergoing maintenance chemotherapy and 2) 12 patients in remission for at least five years in whom chemotherapy had been discontinued at least six months before this study. The first group consistently demonstrated a marked depression in their NK activity and antibody-dependent cell-mediated cytotoxicity (K-cell activity), as compared with normal controls. In contrast, normal levels of cytotoxicity were found in the second group of patients off of all chemotherapy. One patient studied while on chemotherapy and on two occasions following discontinuation of maintenance medications demonstrated that while NK and K-cell activity was depressed during therapy, normal activity returned within days when immunosuppressive therapy was stopped. Thus, present modes of chemotherapy clearly had a profound effect on the in vitro NK and K-cell activity; however, no long-term effect on these functions was noted in our studies.