IL-1 but not TNF is required for the production of IL-17 by human PBMCs cultured in the presence of PGE₂. Culture conditions as in the legend of Figure 1. IL-1Ra (1 μg/mL), TNF-bp (10⁻⁸ M), IL-1β (500 ng/mL), and indomethacin (10⁻⁵ M) were added at the beginning of the culture in the absence of exogenous IL-23 except when mentioned. IL-17, IFN-γ, and IL-1β were assessed by multiplex immunoassay in 7-day culture supernatants. Bars represent the mean plus or minus SD of 6 (A-C) or 4 (D) distinct individual donors. *Significant differences (P < .01) compared with the nil culture condition by paired Student t test.