Differential effects of recombinant interferons alpha, beta, and gamma on induction of human lymphokine (IL-2)-activated killer activity.

The effects of three classes of recombinant interferons (IFN-alpha A, IFN-beta, and IFN-gamma) on maximal induction of lymphokine (IL-2)-activated killer (LAK) activity were studied. Highly purified lymphocytes (greater than 99%) were obtained by counter-flow centrifugal elutriation from peripheral blood of healthy donors. After incubation for 4 days with IL-2 (1 U/ml), purified lymphocytes showed maximal LAK activity against NK cell-resistant target (Daudi) cells, as assessed by 4-hour 51Cr release assay. Addition of exogenous IFN-alpha A or IFN-beta to cultures of lymphocytes plus IL-2 resulted in significant inhibition of LAK activity, but addition of IFN-gamma had no effect on LAK induction by IL-2. IFN-alpha A caused greatest inhibition of LAK activity when added at the start of culture of lymphocytes with IL-2, and was less inhibitory when added 1 day later. Similar inhibition by IFN-alpha A or IFN-beta was observed with nine lines of human tumorigenic cells as targets of LAK activity. IFN-alpha A and IFN-beta also inhibited the proliferative responses of lymphocytes to IL-2 stimulation, and the expression of IL-2 receptors on their surface, whereas IFN-gamma did not. These results suggest that IFN-alpha A and IFN-beta may be important in in situ regulation of LAK cell induction against neoplasms.