HLA-B27 subtypes and tumor necrosis factor α promoter region polymorphism in Iranian patients with ankylosing spondylitis

Abstract: Background. HLA-B27 is an MHC class I molecule that is strongly associated with ankylosing spondylitis (AS). TNF-α, as an important cytokine in inflammatory joint disease, might have a role in the process of AS. This study was performed to determine HLA-B27 subtypes among Iranian patients with AS, and to investigate TNF-α gene polymorphisms in the patient groups. Methods. Ninety seven AS patients (74 HLAB27- positive and 23 HLA-B27-negative) and 137 healthy normal subjects (2 HLA-B27-positive) were enrolled in this study. HLA-B27 positive patients were screened using the polymerase chain reaction, with sequence specific primers (PCR-SSP), for B*27 subtyping. All patients and the controls were also investigated for determination of TNF-α polymorphisms using the same method. Results. Just two subtypes were detected in our patients, namely B*2705 (63.4%) and B*2702 (36.6%). The study of TNF-α polymorphisms at position -238 showed that the A allele and AA genotype were significantly over-represented in all patient groups in comparison with the control group (p < 0.001). At position -308, while the A allele and AA genotype were significantly overrepresented in the whole patient group (p = 0.01), there was no significant difference between the AS groups and the control group. Conclusion. It could be suggested that a polymorphism within the TNF-α gene at -238 play an important role in AS, although this polymorphism was not related to HLA-B27 subtypes. Keywords: ankylosing spondylitis, HLA-B27, MHC class I, polymorphism, TNF-α