In relation to CD4+CD25+ regulatory T cell (Treg), which characteristically express the transcription factor forkhead box protein p3 (Foxp3), Cox et al. reported that IL-27 suppresses differentiation of inducible Treg under IL-2 and transforming growth factor (TGF)-β stimulation and that Foxp3 expression is enhanced by IL-27Rα deficiency in the mouse colitis model induced by transfer of naïve CD4+ T cells [3]. This evidence concerns the gene CD4 and colitis.