[Immunology in medical practice. XXVI. Immunogenetics of chronic inflammatory bowel diseases].

Epidemiological and family studies have shown that the inflammatory bowel diseases (IBD), encompassing ulcerative colitis and Crohn's disease, are in large part genetically determined. This genetic susceptibility is complex and does not follow Mendelian inheritance patterns. The search for susceptibility genes is further complicated by genetic and clinical heterogeneity. Recent developments in molecular biology have enabled the identification of chromosomal regions and genes underlying IBD. Genetic association studies have established a role of HLA genes and cytokine gene polymorphisms in the pathogenesis of IBD. Whole genome linkage analysis studies using microsatellite markers and affected sib-pair analysis have identified two chromosomal locations (IBD1 on chromosome 16 and IBD2 on chromosome 12) associated with IBD. Recent investigations have shown that some chromosomal regions play a role in several autoimmune disorders. This suggests the presence of two types of genes in these diseases: genes that encode proteins that play a key role in the immune response and predisposing for autoimmune diseases in general, and disease-specific genes that are responsible for the phenotype and the severity of the disease.