Genetic Variations in TNFAIP3 and CTLA4 and Their Association with Circulating TNF-α and sCTLA4 Levels in Kurdish...

Background/Objectives: Rheumatoid arthritis (RA) is a chronic autoimmune disease marked by sustained synovial inflammation and systemic immune activation. Genetic polymorphisms in key immune-regulatory pathways are thought to influence both disease susceptibility and progression. This study aimed to characterize sequence variation within selected coding regions of TNFAIP3 and CTLA4 in Kurdish patients with RA and to evaluate circulating TNF-α and soluble CTLA-4 (sCTLA-4) levels in the same cohort. Methods: Eighty-seven participants (67 RA patients, 20 controls) were enrolled. Serum TNF-α and sCTLA-4 concentrations were quantified by ELISA. Genomic DNA was extracted and targeted Sanger sequencing of selected coding regions of TNFAIP3 and CTLA4 was performed in RA patients. Variant identification was conducted relative to GRCh38 and annotated using dbSNP and Genome Aggregation Database (gnomAD). GeneMANIA was used for network-based contextualization. Results: In the 218-bp targeted region of TNFAIP3, 103 sequence-level variant occurrences were identified in RA patients, including substitutions and insertion/deletion events. In the 136-bp targeted region of CTLA4, 33 sequence-level variant occurrences were identified, also including substitutions and insertion/deletion events. RA patients exhibited significantly elevated serum TNF-α levels compared with controls (p = 0.025), whereas sCTLA-4 levels did not differ significantly. Conclusions: This study provides the first targeted characterization of TNFAIP3 and CTLA4 genetic variation in Kurdish RA patients and integrates these findings with circulating inflammatory biomarkers. Although not designed to assess disease susceptibility, the study provides a valuable descriptive genetic resource for this population and complements existing evidence implicating NF-κB regulation and immune checkpoint signaling in RA. These findings establish a strong foundation for future case-control, genotype-phenotype, and functional investigations.