Association of a new allele of the TAP2 gene, TAP2* Bky2 (Val577), with susceptibility to Sjögren's syndrome

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Abstract
Objective. To investigate the polymorphisms of TAP (transporters associated with antigen processing) genes among patients with primary Sjögren's syndrome (SS) in order to clarify the potential association of the polymorphisms with disease susceptibility. Methods. Polymorphisms of the TAP1 and TAP2 genes in 108 Japanese SS patients were determined by analyzing TAP genes using the polymerase chain reaction-single-stranded conformation polymorphism technique. Results. The allelic frequency of the TAP1 gene was not significantly different between SS patients and normal subjects. In addition to all known TAP2 alleles, a new allele (Bky2), which had a unique substitution at codon 577 (ATG→GTG: Met→Val), was identified in both groups. The allelic frequency of Bky2 was significantly higher in SS patients (12.0%) than in normal subjects (5.1%) (P < 0.05). Moreover, a significantly greater frequency of SS-A antibody was found among SS patients with Bky2 (18 of 23; 78%) than among those without Bky2 (33 of 85; 39%) (P = 0.001). Conclusion. The mutation in TAP2 (Val577) may be involved in SS-A autoantibody production and could be a genetic factor that determines susceptibility to SS.