Structural polymorphism and function of HLA-B27.

Over the past year, new subtypes have been described and significant advances have been made in understanding peptide binding to HLA-B27. These developments help in interpreting how antigen presentation is modulated by HLA-B27 polymorphism, in determining the similarities and differences in T cell antigenicity among subtypes, and in finding the basis of HLA-B27 evolution. New insights into the pathogenetic link between enteric bacteria and HLA-B27 come from demonstration of a direct relationship between gut flora and joint inflammation in transgenic rats and from involvement of HLA-B27 in modulating bacterial invasion of mammalian cells. The association between HLA-B27 and spondyloarthropathy may be related to antigen-presenting specificity, but a different mechanism, presentation of a B27-derived peptide by class II antigens, may contribute to the pathogenesis of acute anterior uveitis, emphasizing the need for a comprehensive understanding of the structure, antigenicity, and function of HLA-B27.