IFN-γ production in response to IL-15 and viral infections. PBMC were either treated with rIL-15 (50 ng/mL), EBV, HSV-1, or a combination of virus plus IL-15. On the indicated days, cell-free supernatants were harvested and tested for the presence of IFN-γ using commercial ELISA kits. Results are representative of 3 donors. *P < .05; **P < .02.