Open AccessTwo distinctive HLA haplotypes harbor the B27 alleles negatively or positively associated with ankylosing spondylitis in Sardinia: Implications for disease pathogenesis
Author(s) -
Fiorillo Maria Teresa,
Cauli Alberto,
Carcassi Carlo,
Bitti Pier Paolo,
Vacca Alessandra,
Passiu Giuseppe,
Bettosini Francesca,
Mathieu Alessandro,
Sorrentino Rosa
Publication year - 2003
Publication title -
arthritis & rheumatism
Language(s) - English
Resource type - Journals
eISSN - 1529-0131
pISSN - 0004-3591
DOI - 10.1002/art.10948
Subject(s) - haplotype , allele , ankylosing spondylitis , human leukocyte antigen , genetics , hla b27 , pathogenesis , immunology , hla b , biology , medicine , gene , antigen
Objective To compare haplotype distribution in HLA–B27–positive patients with ankylosing spondylitis (AS) and healthy control subjects possessing either AS‐associated HLA–B27 alleles or the non–AS‐associated HLA–B*2709 allele. Methods DNA samples from 47 HLA–B27–positive patients with AS and 76 HLA–B27–positive healthy controls (19 positive and 57 negative for B*2709) living in different areas of Sardinia were collected and typed for HLA class I and class II alleles. The third exon of the B27 gene was analyzed for the presence of Asp 116 or His 116 , which differentiates B*2709 from the other two B27 subtypes (B*2705 and B*2702) that are mostly found in Sardinia. The parents of 6 subjects positive for B*2709 were also typed for HLA class I and class II alleles. Statistical analysis was performed by Fisher's exact test. Results In Sardinia, the B27 alleles conferring susceptibility to AS appear to be more frequently carried by a haplotype (A2;B27;Cw2;DR16) that reaches its highest frequency in patients with AS (A2 80.8%, B27 100%, Cw2 83%, and DR16 74.5%). Conversely, the non–AS‐associated B*2709 allele is more frequently found together with other HLA alleles whose frequencies are inversely correlated with the disease (A32 or A30, Cw1, and DR12). Familial analysis of 6 subjects positive for HLA–B*2709 confirmed the existence of a “Sardinian” haplotype that is not associated with AS (A32;B*2709;Cw1;DR12). Conclusion In Sardinia, 2 distinct haplotypes harbor the non–AS‐associated HLA–B*2709 allele or the AS‐associated B27 alleles. Our findings are compatible with the hypothesis that other genes within the HLA region besides HLA–B27 may play some role in conferring susceptibility to AS.