Evidence of immunological dysfunction in CIE also includes the expression of mucosal nitrite, a precursor of the inflammatory mediator of nitric oxide (NO) in dogs with idiopathic IBD (85) and increased numbers of inducible nitric oxide synthase (iNOS)-expressing cells associated with PAS+ macrophages in biopsies of dogs with GC (86). This evidence concerns the gene NOS2 and irritable bowel syndrome.