The response to interferon of NK and K cells from conventionally immunosuppressed and cyclosporine-treated renal allograft recipients.

Interferon is a potent stimulator of natural killer (NK) and killer (K) cell activity in human beings, both these cytotoxic functions representing host defense mechanisms against viral infections and lymphoid malignancy. Both NK and K cell functions are markedly impaired in conventionally immunosuppressed allograft recipients but coincubation of lymphocytes from these patients with purified human lymphoblastoid interferon considerably augments both these activities. Cyclosporine immunosuppression causes only a moderate, but significant, impairment of NK activity--but K cell activity appears to be normal. Again IFN increases NK activity of the lymphocytes of these patients but produces a fall or only moderate increases in K cell activity. We conclude that these data support the functional distinction between NK and K cells and suggest that immunosuppressive agents act at the pre-NK/K cell stage of maturation, though possibly via different mechanisms.