CD4 and colitis: Although this study cannot exclude the possible contribution of PI3K in non-T cells to Th17 differentiation, adoptive transfer of p85α-deficient naive CD4+ T cells in murine T-cell transfer model of colitis shows decreased Th17 differentiation compared to wild-type CD4+ T cells, with Th1 differentiation maintained (our unpublished observations), indicating the pivotal roles of PI3K in CD4+ T cells in in vivo Th17 differentiation.