The resulting clustering of HLA-DRB1 alleles (encoding these molecules) showed that alleles associated with increased risk of IBD generally fell into different clusters than alleles associated with decreased risk of IBD, suggesting that the HLA-DR molecules associated with increased risk of IBD exhibited structural and electrostatic properties within the peptide-binding grove that were largely distinct from those associated with decreased risk. This evidence concerns the gene HLA-DRB1 and inflammatory bowel disease.