This homeostasis is mediated by the integrity of the intestinal barrier and a functional immunotolerance to intestinal microbiota and luminal antigens. NOD2, the first gene identified for IBD susceptibility, represents an example of a mechanism by which inflammatory disease is propagated by a dysregulated response to the symbiotic microbiota [3, 4, 9]. The gene discussed is NOD2; the disease is inflammatory bowel disease.