Current theories on the causes of inflammatory bowel disease.

The understanding of the pathogenesis of CD and UC has greatly expanded over the last decade. The combination of abnormalities in the immune system, the contribution of nonimmune cells in the intestinal mucosa, a variety of genetic risk determinants, and random environmental factors may all be necessary to induce what clinically presents as IBD. It is likely that several agents can initiate an immune response that in the intestinal microenvironment and the genetic background of the patient finally leads to pathology.