Amino acid position 11 of HLA-DRbeta1 is a major determinant of chromosome 6p association with ulcerative colitis.


The major histocompatibility complex (MHC) on chromosome 6p is an established risk locus for ulcerative colitis (UC) and Crohn’s disease (CD). We aimed to better define MHC association signals in UC and CD by combining data from dense single-nucleotide polymorphism (SNP) genotyping and from imputation of classical human leukocyte antigen (HLA) types, their constituent SNPs and corresponding amino acids in 562 UC, 611 CD and 1428 control subjects. Univariate and multivariate association analyses were performed, controlling for ancestry. In univariate analyses, absence of the rs9269955 C allele was strongly associated with risk for UC (P = 2.67 x 10(-13)). rs9269955 is a SNP in the codon for amino acid position 11 of HLA-DRbeta1, located in the P6 pocket of the HLA-DR antigen binding cleft. This amino acid position was also the most significantly

Genes and immunity