Kinetic studies for the inhibition by IL-10 and IL-4 of PGE₂ production in LPS-stimulated neutrophils. Human neutrophils (1 × 10⁶ cells) were cultured for 24 hours with or without 10 ng/mL of IL-10 or IL-4 in the presence 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 two separate experiments.