Abdullah AbdulKareem Ahmed Al-Obaidi, Farah Thamer Samawi, Mehmet Gökhan Halıcı
Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by persistent inflammation and progressive joint destruction. Increasing evidence suggests that fungal dysbiosis may influence immune responses through the interleukin-17A (IL-17A) pathway. This study aimed to determine the prevalence of peripheral blood Candida albicans DNA in patients with RA, quantify serum IL-17A concentrations, and evaluate the association between fungal DNA positivity and IL-17A levels. A total of 100 participants, including 50 patients with RA and 50 healthy controls, were enrolled. Candida albicans DNA was detected by conventional polymerase chain reaction (PCR) targeting the INT1 gene, while serum IL-17A concentrations were measured using enzyme-linked immunosorbent assay (ELISA). The association between fungal DNA positivity and serum IL-17A concentrations was assessed using point-biserial correlation analysis. Candida albicans DNA was detected significantly more frequently in RA patients than in healthy controls (38% vs. 10%; p < 0.001). Serum IL-17A concentrations were significantly higher in RA patients, with the highest levels observed in C. albicans-positive patients (46.2 ± 8.7 pg/mL), followed by C. albicans-negative RA patients (32.5 ± 6.4 pg/mL) and healthy controls (15.1 ± 5.2 pg/mL) (p < 0.001). Point-biserial correlation analysis demonstrated a significant positive association between C. albicans DNA positivity and serum IL-17A concentrations (rpb = 0.672, p < 0.001). Peripheral blood Candida albicans DNA positivity was associated with elevated serum IL-17A concentrations in patients with RA. These findings support an association between fungal DNA detection and enhanced IL-17A-mediated immune responses; however, the cross-sectional design precludes any inference of causality. Further longitudinal studies incorporating quantitative fungal detection are warranted.