Introduction: The result of recent genome-wide association studies revealed that, in addition to HLA-B27, a few non-HLA genes are associated with susceptibility to ankylosing spondylitis (AS) in Caucasian populations. According to these studies, IL-23R is one of the genes that is associated with AS. In this study, we evaluated five important single nucleotide polymorphisms (SNPs) of the IL-23R gene which confers susceptibility to AS, and its effects on the severity of the disease in HLA-B27 positive and negative patients and several subtypes of HLA-B27.
Materials and methods: The study population consisted of 294 AS patients and 352 age-, sex-, and ethnicity-matched healthy controls. All patients were examined by rheumatologists, and met modified, New York criteria for the disease. Five SNPs (rs1004819, rs11209032, rs1495965, rs11465804, and rs1004819) of the IL-23R gene were genotyped using the Real-Time PCR TaqMan genotyping method.
Results: We found that only rs1004819 has a significant association with AS, and that the remaining four SNP alleles are not associated with AS. Also, there was no association between these five polymorphisms and BASDAI, BASFI, and BASMI indices. Two haplotypes, ACGAT and ACGAG, were found to be associated with the heritability of AS. In addition, two significant, protective diplotypes (D8, GCGAG/GTGGG ; and D9, ACGAG/GCGAG) were discovered.
Conclusion: This study supported our previous findings regarding the differences between the genetic patterns of AS in Iranian patients compared with those in other parts of the world.
Keywords: HLA-B27; IL23R; SNP; ankylosing spondylitis.