HLA-A and -B antigens in inflammatory bowel disease.

We examined all available data on HLA-A and -B antigen distributions in patients with Crohn's disease and ulcerative colitis. The risk of Crohn's disease was significantly increased in individuals with HLA-A2, having a relative risk of 1.25, in 730 pooled Caucasoid patients compared with 10 863 pooled controls, and decreased in individuals with HLA-A11, having a relative risk of 0.62. The risk of ulcerative colitis was also significantly increased in individuals with HLA-B27 and -Bw35, having a relative risk of 1.81 and 1.41 respectively, in 560 pooled Caucasoid patients compared with 6151 pooled controls, whilst in 144 pooled Japanese patients who were compared with 442 pooled controls, the risk of colitis was increased in individuals with HLA-B5 with a relative risk of 2.79. All differences remained significant after correction for the number of antigens examined. The bases for these genetic associations are unclear.