IL-1RI⁺ naive CD4⁺ T cells produce higher levels of IL-17 in response to a combination of IL-1β and TCR triggering. (A) Flow cytometric analysis of intracellular IL-17 and IFN-γ in sorted IL-1RI⁺ and IL-1RI⁻ naive CD4⁺ T cells that were stimulated for 7 days in serum-free media with anti-CD3/anti-CD28 antibody-coated beads in the presence or absence of IL-1β followed by 16 hours of PMA and ionomycin stimulation. (B) ELISA of IL-17 production from sorted IL-1RI⁺ and IL-RI⁻ naive CD4⁺ T cells that were stimulated as described in panel A. (C) RT-PCR analysis of Th17-related genes in sorted IL-1RI⁺ and IL-1RI⁻ naive CD4⁺ T cells that were stimulated as in panel A. Results are relative to the number of transcripts encoding β-actin. Data represent 4 separate experiments (A, 1 experiment per donor) or are from 4 (B) and 3 (C) donors; error bars, mean ± SD (B) or ± SEM (C) of triplicates.