[HLA-B27 molecular subtypes and spondylarthropathies]

The close association between HLA-B27 and spondyloarthropathies remains unexplained. Twelve HLA-B27 subtypes designated B*2701 to B*2712 have been described in various populations. Variations in the ability of these alleles to carry susceptibility to spondyloarthropathies may exist, and may be ascribable to differences in endogenous peptide presentation. This hypothesis was evaluated by a study of peptide-binding motifs of endogenous peptides extracted from various HLA-B27 alleles. A peptide motif with a tyrosine residue at the C-terminus was not characteristic of HLA-B27 subtypes carrying susceptibility, consistent with the known lack of association of B*2707 with spondyloarthropathies. However, at the level of the individual, differences may exist between endogenous peptides presented by subtypes that do and do not confer susceptibility.