PTPN22, PDCD1 and CYP27B1 polymorphisms and susceptibility to type 1 diabetes in Polish patients.

Type 1 diabetes (T1DM) is a common autoimmune disease with a complex genetic background. This study was aimed to investigate the association of PTPN22 G(-1123)C and C1858T, PDCD1 G7146A and CYP27B1 C(-1260)A polymorphisms with T1DM among Polish subjects. The PTPN22 gene encodes lymphoid tyrosine phosphatase, a potent negative regulator of T cell activation. PDCD1 gene gives rise to an inhibitory cell-surface receptor, expressed on activated lymphocytes. CYP27B1 encodes 1-alpha hydroxylase, responsible for conversion of the vitamin D(3) precursor into its active form, involved in the immune function. Polymorphic variants of these genes have previously been associated with various autoimmune disorders. The four polymorphisms were genotyped by PCR-restriction fragment assays in a case-control study comprising 215 T1DM patients and 236 healthy controls. The PTPN22 T1858 allele appeared significantly increased in T1DM compared to the control group (P=0.004), yielding an OR of 1.73 (95% CI 1.19-2.51). The difference in distribution of C1858T genotypes also demonstrated statistical significance (P=0.015). The frequencies of PTPN22 G(-1123)C alleles and genotypes did not differ between T1DM cases and controls, although the haplotype comprising both mutant PTPN22 alleles, C(-1123) and T1858, was significantly more frequent in affected individuals (P=0.003). G(-1123)C and C1858T were in linkage disequilibrium (D' = 0.98; r(2) =0.61 in T1DM and D' = 0.97; r(2) =0.41 in controls). No significant differences in the allele and genotype frequencies of PDCD1 and CYP27B1 polymorphisms were found between patients and controls. This study confirms the association of PTPN22 C1858T polymorphism with T1DM, whereas the effects of PTPN22 G(-1123)C, PDCD1 G7146A and CYP27B1 C(-1260)A seem unlikely, at least in the Polish population.