HLA-DR and -DQ phenotypes in inflammatory bowel disease: a meta-analysis

Background-Susceptibility to inflammatory bowel disease (IBD) is partially genetically determined and the HLA class II genes are candidates for a role in genetic susceptibility to IBD, because their products play a central ro le in the immune response. Multiple studies have reported associations betw een HLA-DR or -DQ phenotypes and either ulcerative colitis or Crohn's disea se, but much of the data are still controversial. Aims-To estimate overall associations between HLA class II phenotypes and I BD, and to establish the relative risk conferred by HLA-DR and -DQ phenotyp es by meta-analysis, Methods-Medline was searched for publications reporting on the relation bet ween IBD and HLA class II phenotypes. Raw data were extracted by recalculat ing the number of phenotypes or the number of alleles of the main antigens. Odds ratios and confidence intervals were calculated according to the Mant el-Haenszel method. Results-DR2, DR9, and DRB1*0103 were positively associated with ulcerative colitis, and a negative association was found for DR4 and ulcerative coliti s. For Crohn's disease a positive association was found with DR7, DRB3(star )0301, and DQ4 and a negative association with DR2 and DR3. Conclusions-Both ulcerative colitis and Crohn's disease are associated with specific HLA class II phenotypes. Further analysis of these phenotypes and subgroup analysis may elucidate how these alleles contribute to susceptibi lity to IBD.