Assessment Levels of IL-22 in Rheumatoid Arthritis Patients in Najaf City

Rheumatoid arthritis (RA) is a chronic, T cell–driven autoimmune disease characterized by persistent synovial inflammation, joint pain, swelling and stiffness, and often leads to structural deformities. Beyond the joints, RA may involve extra-articular organs such as the heart, lungs, kidneys and digestive tract, contributing to considerable morbidity. In this study, we sought to explore the role of interleukin-22 (IL-22)—a cytokine primarily produced by activated T cells—in RA by comparing its serum levels in patients and healthy volunteers alongside established immunological markers. We conducted a case–control study in which venous blood was drawn from two groups: 30 patients meeting the 2010 ACR/EULAR criteria for RA and 30 age- and sex-matched healthy controls.Complete blood count (CBC) parameters—including white blood cell count (WBC), hemoglobin (Hb), packed cell volume (PCV), and platelet count (PLT)—were measured using an automated analyzer. Serum IL-22 and anti–cyclic citrullinated peptide (anti-CCP) antibody concentrations were measured by enzyme-linked immunosorbent assay (ELISA), while rheumatoid factor (RF) IgM and C-reactive protein (CRP) levels were determined using the I-Chroma system. Statistical analyses employed Student’s t-test for continuous variables and chi-square test for proportions, with p < 0.05 considered significant. Patients with RA exhibited a mean serum IL-22 level of 173.9 ± 51.2 pg/mL, which was significantly lower than the 216.3 ± 84.6 pg/mL observed in healthy controls (p = 0.001).RA patients also had significantly lower WBC (6.89 ± 1.86 vs. 8.21 ± 2.90 ×10³/μL; p = 0.039) and platelet counts (241.4 ± 42.3 vs. 287.0 ± 84.1 ×10³/μL; p = 0.040), and higher Hb levels (12.54 ± 1.46 vs. 11.38 ± 2.00 g/dL; p = 0.030). RF IgM positivity was more frequent in the RA group (43.3%) compared with controls (13.3%; p = 0.005), and CRP levels were markedly elevated in RA patients (14.90 ± 7.17 IU/dL) versus controls (4.58 ± 1.50 IU/dL; p < 0.001). Anti-CCP antibodies were detected in 96.7% of RA patients and in 0% of controls (p < 0.001). Although IL-22 levels correlated with RF and CRP, these exploratory data do not yet establish IL-22 as a reliable biomarker; further longitudinal and mechanistic studies are needed to clarify its potential role in RA diagnosis and monitoring. Keywords: Rheumatoid Arthritis (RA), RF, Anti-ccp, IL22