Natural killer cell activity in renal transplant recipients receiving cyclosporine

Abstract

Normal subjects (11) had a mean circulating natural killer (NK) cell activity of 188 lytic units/107 peripheral mononuclear blood leukocytes. This activity was significantly enhanced by in vitro incubation with 500 U of .alpha.-interferon (+207 lytic units). The mean NK activity of renal transplant recipients on azathioprine (17), or on cyclosporine (17), studied at various times after transplantation was significantly decreased, as was the ability of interferon to enhance NK activity. In the cyclosporine group, interferon could not enhance NK titers 1-6 wk after transplantation when the patients were on the highest doses of cyclosporine (mean, 1002 mg/day) or when they were viremic for cytomegalovirus. After 18 wk, when the patients received 546 mg/day or when viremia was no longer detected, the ability of interferon to enhance NK activity was more normal. Cyclosporine and cytomegalovirus infection may have a greater effect on the action of interferon on NK activity than on the NK titer per se. This defect may diminish the reserve of NK cells and contribute to post-transplant immunosuppression.