Background HLA-B27 is strongly associated with ankylosing spondylitis (AS) and most studies in the last years suggest that B27 molecule itself could be directly involved in the aetiology of AS. On the other hand, some studies suppose existence of additional gene involved in AS. That gene could also be located inside the HLA region.
Objectives The aim of this study was to analyse the polymorphism at neighbouring HLA-loci in the group of B27 positive AS patients and B27 positive unrelated healthy individuals.
Methods All 52 B27 positive AS patients and 32 B27 positive controls were DNA typed for B27 subtypes, Cw and DRB1 alleles by PCR-SSP method.
Results Three different ancestral haplotypes were found in the patient group: B*2705-Cw*0202 (82.3%), B*2705-Cw*0102 (13.8%), and B*2705-Cw*0202 (6.9%). Comparison between patients and controls did not show any significant differences. Analysis of distribution of DRB1 alleles revealed that DRB1*01 allele was the most present allele among B*27 positive individuals (21.5% in AS group and 23.4% in control group). DRB1*0301 allele was significantly more frequent in patients than in controls (9.6% vs. 1.6%; p = 0.03), while lower frequency of DRB1*0701 allele among patients is marginally significant (1.9% vs 7.8%; p = 0.055). Furthermore, the linkage disequilibrium between observed between second most frequent allele (DRB1*16) and B*27 has to be noted as characteristic for our population.
Conclusion Our results suggest that HLA-Cw alleles are not involved in aetiology of AS. The possible role of some DRB1 alleles, as well as non HLA markers around HLA-B locus in necessary to confirm on a larger group of B27 positive individuals.