Regulation by IL-4 and IFN-γ of IL-8 production in IL-15–stimulated monocytes. Monocytes were incubated with medium alone or supplemented with IL-15 (1,000 ng/m), IL-4 (100 U/mL), IFN-γ (500 U/mL), IL-15 plus IL-4, or IL-15 plus IFN-γ. After 6 hours supernatants were assayed for IL-8 content by ELISA. Results represent mean ± SE of IL-8 concentrations of three independent experiments. *Significant difference of IL-8 concentration (P < .05). †Significant inhibition by treatment (P < .05).