Effect of iNOS inhibitors on IL-2–induced IFN-γ production by PB- and S-NK cells. PB-NK and S-NK cells were incubated with or without IL-2 for 18 (□) or 96 hours (▪), respectively, in the presence or absence of AG (10 μmol/L) or L-NMMA (500 μmol/L). After incubation, cell-free supernatants were collected and IFN-γ levels quantitated by ELISA.