To determine whether the amount of IFN-α2 detected in HCMVsn during the first 24 h of infection could alone mediate the same increases in NK cell cytotoxicity as HCMVsn, we compared NK cell natural and antibody-dependent cytotoxic activity in response to HCMVsn or purified recombinant IFN-α2. The gene discussed is IFNA2; the disease is infection.