B27 polymorphism and peptide repertoire.

Over 130 HLA-B alleles have been defined at the level of nucleotide sequence. Nine of these are subtypes of HLA-B27. To understand how HLA-B27 predisposes towards arthritis it is important to determine which B27 subtypes are associated with disease susceptibility and which are not. A characteristic of HLAB27 is the binding of peptides having arginine at position 2. However, HLA-B*7301, a rare and unusual allele of European populations, has an identical "B" subpocket to B*27 and also binds peptides with arginine at position 2. The association of the Bw4 public epitope with inhibition of certain NK cells raises the possibility that NK cell responses may contribute to HLA-B27-associated disease.