Effect of interferon alpha on natural killer cell cytotoxicity in kidney transplant recipients.

Natural killer (NK) cell cytotoxicity was monitored in 32 kidney transplant recipients during a double-blind, placebo-controlled trial of interferon alpha prophylaxis. During the first month following transplantation, NK cytotoxicity diminished in both interferon and placebo-treated patients. Thereafter, mean values for NK cytotoxicity decreased further in interferon recipients, whereas they returned toward baseline in placebo recipients. Paradoxically, interferon alpha consistently augmented NK cytotoxicity of all patients in vitro. Various immunosuppressive regimens were employed in these patients. NK cytotoxicity was slightly diminished in patients receiving prednisone and azathioprine, moderately depressed in those who received prednisone, azathioprine, and OKT3 antibody. Three or four placebo recipients with clinically severe cytomegalovirus (CMV) infections had diminished NK cell function. These studies indicate that a variety of factors including exogenous interferon, immunosuppressive regimens, and CMV infections can influence NK cytotoxicity in renal transplant recipients.