CD4 and colitis: Enhances antigen presentation by upregulating MHC II, CD80, and CD86; phagocytosed by APCs and displayed on MHC II to activate CD4+ T cells in a TLR2-dependent manner; corrects CD4+ T cell deficiencies and TH1/TH2 imbalance in germ-free mice by upregulating the production of IFN-γ+ TH1 T cells through CD11c+ DCs and the IL-12/STAT4 pathway; represses TH17 responses; induces IL-10 producing FoxP3+ Tregs in a TLR2-dependent manner; protects against TNBS-induced colitis and Helicobacter hepaticus-induced colitis; OMVs