The Relationship between IL-22 and interstitial lung disease in patients with rheumatoid arthritis

Abstract Background Interstitial lung disease (ILD) is a common and severe extra-articular manifestation of rheumatoid arthritis (RA), contributing significantly to patient morbidity and mortality. Recent studies have identified interleukin-22 (IL-22) as a cytokine implicated in immune regulation and fibrotic processes in various organs, including the lungs. However, its specific role in RA-associated ILD (RA-ILD) remains unclear. Understanding this relationship may offer insights into novel biomarkers and therapeutic strategies. Methods A cross-sectional study was conducted on 20 RA patients with ILD, 20 RA patients without ILD, and 20 age and gender-matched healthy controls. ILD was confirmed via high-resolution chest computed tomography (HRCT). Serum IL-22 concentrations were measured using enzyme-linked immunosorbent assay. Disease activity was assessed using the DAS28 score, ESR, CRP, and ILD severity were analyzed. Results IL-22 concentrations were considerably higher in RA-ILD patients (1309; IQR 943.85–1600) in comparison to RA patients without ILD (321; IQR 213.3–449.4) and healthy controls (64.78; IQR 54.3–72.08) (p < 0.001). IL-22 levels correlated positively with disease activity score 28 (DAS28), ESR, and CRP. Elevated IL-22 concentrations were also associated with more severe ILD, as indicated by the Warrick scores (p = 0.022). Receiver operating characteristic(ROC) analysis demonstrated a cut-off value of 651.7 ng/L for IL-22 with 90% specificity and 85% sensitivity (AUC = 0.92). Elevated IL-22 levels and smoking were found to be independent predictors of ILD in RA patients. Conclusions Serum IL-22 levels are significantly increased in RA-ILD patients and are associated with disease activity and ILD severity. Elevated IL-22 and smoking may serve as essential predictors of ILD in RA. IL-22 may also serve as a valuable biomarker for early detection as well as a potential treatment target in RA-ILD.