In patients suffering from Crohn’s disease, which can affect the entire gastrointestinal tract, we found increased serum levels of PGD2 and its metabolite Δ(12)-PGJ2, and in a corresponding mouse model of colitis induced by 2,4,6-trinitrobenzenesulfonic acid, the CRTH2 antagonist timapiprant ameliorated inflammation via inhibition of pro-inflammatory mediators TNF-α, IL-1β and IL-6 [67]. The gene discussed is PTGDR2; the disease is colitis.