Prostaglandin E2-EP4 signaling promotes immune inflammation through TH1 cell differentiation and TH17 cell expansion

Two distinct helper T (T-H) subsets, T(H)1 and T(H)17, mediate tissue damage and inflammation in animal models of various immune diseases such as multiple sclerosis, rheumatoid arthritis, inflammatory bowel diseases and allergic skin disorders. These experimental findings, and the implication of these TH subsets in human diseases, suggest the need for pharmacological measures to manipulate these TH subsets. Here we show that prostaglandin E-2 (PGE(2)) acting on its receptor EP4 on T cells and dendritic cells not only facilitates T(H)1 cell differentiation but also amplifies interleukin-23-mediated T(H)17 cell expansion in vitro. Administration of an EP4-selective antagonist in vivo decreases accumulation of both T(H)1 and T(H)17 cells in regional lymph nodes and suppresses the disease progression in mice subjected to experimental autoimmune encephalomyelitis or contact hypersensitivity. Thus, PGE(2)-EP4 signaling promotes immune inflammation through T(H)1 differentiation and T(H)17 expansion, and EP4 antagonism may be therapeutically useful for various immune diseases.