The role of PTPN22 rs2476601 and STAT4 rs7574865 gene polymorphism in the incidence of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory condition that often affects many peripheral joints. It is characterized by a faulty immune system. This autoimmune disorder affects 1% of the population, with women having double the risk as men. Numerous signs point to the idea that genetics play an important role in the beginning of RA. Previous studies reported that some of the non HLA genes such as PTPN22 and STAT4 could be risk factors for the development of autoimmune diseases, including RA. The purpose of this study was to demonstrate the relationship between the single nucleotide polymorphisms, PTPN22 rs2476601 and STAT4 rs7574865, and a higher risk of RA illness in the population of AL-Dewaniya, Iraq as well as the possibility of galectin 3 associating with the minor allele. One hundred and fifty participants were involved in this study; seventy-five of them were RA patients and the others were clinically healthy control. Blood samples were collected from both study groups and separated into 2 mL in EDTA tubes for genotypic study and 3 mL in gel tube for serological study (Gal-3). According to the results obtained, the frequencies of ofPTPN22 rs2476601 G allele were 73 out of 150 (48.7%), 94 out of 150 (62.7%), while the frequencies of PTPN22 rs2476601 A allele were 77 out of 150 (51.3%) and 56 out of 150 (37.3%) for RA and control respectively. The most prevalent genotype of PTPN22 gene frequency was heterozygous (GA) followed by homozygous mutant (AA), then homozygous wild-type (GG). The STAT4 rs7574865 G allele frequencies were 121 out of 150 (80.7%), 139 out of 150 (92.3%), whereas the STAT4 rs7574865 T allele frequencies were 29 out of 150 (19.3%) and 11 out of 150 (7.3%) for RA and control respectively. The most prevalent genotype of STAT4 gene frequency was the homozygous wild-type (GG) followed by the heterozygous (GT), then the homozygous mutant (TT). The observed results indicate that there is an association between PTPN22 minor allele (A) and STAT4 minor allele (T) with RA. Additionally, for the first time, the study investigated the relationship between Gal-3 (positive results) with minor alleles of the both genes, which shows an association between both minor alleles of both genes' polymorphism and high serum levels (positive results) of galectin-3 (Gal-3).