Associations of the PTPN22 and CTLA-4 genetic polymorphisms with Taiwanese ankylosing spondylitis

Ankylosing spondylitis (AS) is an autoimmune disease, and the imbalance of peripheral tolerance is involved in its pathogenesis. Importantly, the negative signal of activated T cells plays a crucial role in the balance of peripheral tolerance. It has been postulated that human protein tyrosine phosphatase nonreceptor 22 (PTPN22) and cytotoxic T-lymphocyte antigen-4 (CTLA-4) genes encode proteins that are actively involved in regulating T-cell activation. Therefore, we evaluated the effects of PTPN22 and CTLA-4 genotypes on the occurrence of AS. Genetic polymorphisms of PTPN22 -1123G/C and CTLA-4 +49A/G were identified by polymerase chain reaction for 391 AS patients and 391 healthy controls. Subjects with PTPN22 CC and GC genotypes had a greater risk of AS occurrence than those with PTPN22 GG genotype [relative risk = 1.39, 95 % confidence interval (95 % CI) 1.03-1.88]. Further, subjects with PTPN22 CC/CTLA-4 AA or PTPN22 GC/CTLA-4 AA genotypes had 1.90-fold (95 % CI 1.02-3.49) greater risk of AS development than those with other combinations of PTPN22 and CTLA-4 genotypes. Our findings indicated that PTPN22 -1123G/C and CTLA-4 +49A/G genetic polymorphisms have a combined effect on the development of AS.