TAP1 and TAP2 polymorphism in Spanish patients with ankylosing spondylitis.

Objective: HLA-B27 is strongly associated with ankylosing spondylitis (AS); however, the association is not absolute and additional susceptibility factors in the MHC region could play a role. We studied the influence of polymorphism in the transporter associated with antigen processing (TAP) genes, including point mutations not previously analyzed.

Methods: HLA-B*27 typing and subtyping as well as TAP1 and TAP2 typing were performed by PCR-RFLP. Forty-four AS individuals were compared to 61 ethnically matched random individuals and 35 B*27-positive healthy unrelated individuals as controls.

Results: The frequency of the TAP1B allele was significantly greater in the patient group compared with the random controls (corrected p value (p(c)) = 0.035; odds ratio = 15.8, p = 0.01). A greater frequency was also evident when B*27-positive patients and B*27- positive healthy controls were compared, although it did not reach statistical significance. No differences were observed in TAP2 alleles between the groups studied.

Discussion: We did not find a primary association between TAP2 polymorphism and AS susceptibility. Formal confirmation of a linkage between the TAP and HLA-B loci would probably require family studies.