After treatment with DSS, eosinophil-deficient (PHIL) mice exhibited increased colitis severity (Extended Data Fig. 5b,c) and stronger T helper 17 cell (TH17) responses relative to their wild-type littermates, as well as increased production of TNF and IFNγ by CD4+ T cells25 (Extended Data Fig. 5d). This evidence concerns the gene CD4 and colitis.