IL-1β promotes IL-17 production from IL-1RI⁺ and IL-1RI⁻ memory CD4⁺ T cells. (A) ELISA of IL-17 production from sorted IL-1RI⁺ and IL-1RI⁻ memory CD4⁺ T cells that were incubated for 7 days with anti-CD3 and anti-CD28 antibody-coated beads in the presence or absence of IL-1β. (B) Flow cytometric analysis of intracellular IL-17 and IFN-γ in sorted IL-1RI⁺ and IL-1RI⁻ memory CD4⁺ T cells that were incubated and stimulated as in panel A followed by 4 hours of PMA and ionomycin stimulation. Numbers in quadrants indicate the frequency of cells for each quadrant. Data represent the mean ± SEM of 5 donors (A) or 7 separate experiments (B, 1 experiment per donor). P values were obtained by the paired t test.