CD4 T cells with the ability to produce the pro-inflammatory cytokine interleukin (IL)-17, designated Th17 [1], [2], [3], act as co-ordinators of the innate and adaptive immune responses to bacteria and fungi, in particular Candida albicans[4], and have been implicated in several autoimmune diseases, such as multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus, psoriasis and Crohn's disease [5]. This evidence concerns the gene IL17A and Crohn disease.