Decreased cytotoxic potential of fresh and recombinant interleukin 2-cultured large granular lymphocytes in childhood acute lymphoblastic leukemia.

Cytotoxic potential (cytotoxic efficiency and binding affinity) of large granular lymphocytes (LGL) in childhood acute lymphoblastic leukemia (ALL) patients was calculated by Michaelis-Menten's kinetic equation. Cytotoxic efficiency (Vmax) of fresh or 3-day recombinant interleukin 2 (IL-2)-cultured LGL, not of similarly cultured T cells, in on-therapy ALL patients was decreased (31% in fresh LGL, P less than 0.05 and 28% in cultured LGL, P less than 0.01) as compared with that in controls, although the binding affinity (Km) of these cells were not decreased. The cytotoxic efficiency and the binding affinity of IL-2-cultured LGL in off-therapy ALL patients was not decreased. These data indicate that the cytotoxic potential of LGL was selectively decreased in on-therapy ALL patients due to the impairment in the post-binding cytotoxic process, not due to the decrease in the binding affinity.