Analysis of natural killer cell defects in childhood acute lymphoblastic leukemia.

The natural killer (NK) activity of circulating lymphocytes of 38 children with acute lymphoblastic leukemia (ALL) in complete remission was studied by 51Cr-release cytotoxicity assay. NK activity of the non-T-cell fraction (NKnon-T) and of the T-cell fraction (NKT) was also measured. In addition, the number of circulating NK cells was determined by an immunofluorescence technique using monoclonal anti-Leu-7 (HNK-1) antibody. Total NK activity of the ALL patients in complete remission was impaired during maintenance therapy (P less than 0.001) and after cessation of therapy (P less than 0.05). NK activity of NKnon-T and NKT cells was equally impaired (P less than 0.05). The numbers of Leu-7+ cells and NK activity units were decreased during maintenance therapy (P less than 0.05), but approached normal after cessation of therapy. These data indicate that decreased NK activity of childhood ALL in complete remission during maintenance therapy is due to a decrease in total NK cells and impaired function of both NKnon-T and NKT cells.