Immunogenetic Susceptibilities in Inflammatory Bowel Disease

It is now clear that the major identified risk factor for theinflammatory bowel diseases (IBDs) is a positive family history. Furthermore, theavailable data in spouses and twins indicate that the genetic susceptibility is duein large measure to shared familial predisposition. This emphasizes the importanceof identifying the actual familial susceptibilities. Given the data forimmunopathogenetic etiologies in the genesis of IBD, the logical candidate genesare those that involve the immune system. Data for several of these gene markersystems have been considered confusing or inconclusive. When approached withthe concept that IBD is a genetically heterogeneous group of disorders, patternsare beginning to emerge for the human lymphocyte antigen class II region geneson chromosome 6, and the complement C3 gene on chromosome 19. Availabledata do not yet implicate the immunoglobulin or T cell receptor genes, butfurther studies are needed, especially for the latter. Firm identification of geneticsusceptibilities will require the study of an adequate number of families, which isbeing facilitated by the establishment of an IBD family-based cell line bank.Identification of the genes that predispose to IBD will allow the study of naturalhistory from susceptibility to clinical disease and, when understood, will providenew approaches to disease therapy and even prevention