Effects of IL-10 and IL-4 on neutrophil-derived PGE₂ production. Human neutrophils (1 × 10⁶ cells) were cultured for 24 hours with the indicated concentrations of IL-10 and IL-4 in the presence or absence of LPS (100 ng/mL). RIA for PGE₂ was performed as described in Materials and Methods. Results are expressed as the mean ± SEM of triplicate cultures. Similar results were obtained in three separate experiments. *P < .05, **P < .01 (compared with LPS only).