Abstract: Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by progressively destructive joint inflammation and destruction of articular cartilage, bone and synovial hyperplasia. Cytokines play a fundamental role in the processes that cause inflammation, articular destruction and extra-articular manifestations associated with RA. The preferential production of interleukin 22 (IL22) by T cells suggests that elevated levels of this cytokine exist in chronic, T cell-mediated diseases, such as psoriasis and RA and that IL-22 plays an important role in the pathogenesis of these disorders.
Objective: To study the role of IL-22 in RA.
Methods: IL-22 serum levels were measured in 55 female patients with RA, 28 of them on medical treatment and the other 27 were newly diagnosed patients and in 18 healthy controls. Patients are assessed for clinical and laboratory variables. Correlations of IL-22 serum levels with disease activity markers as disease activity score for 28 joints (DAS28), serological markers, bone erosions were assessed.
Results: IL-22 levels were increased in patients with RA compared with controls (mean 34.6 pg/ml and 3.2 pg/ml, respectively; P < 0.001). Levels of IL-22 correlated positively with DAS28 score (P < 0.001). C-reactive protein (CRP) correlated positivity with high levels of IL-22 in RA patients (mean 53.8 pg/ml; P < 0.001) and rheumatoid factor (RF) correlated positivity with high levels of IL-22 in RA patients (mean 46.1 pg/ml; P < 0.001). The presence of bone erosions was associated with high IL-22 levels (P = 0.008).
Conclusion: IL-22 is elevated in the serum of patients with RA. Elevated serum IL-22 allows discrimination between patients with different clinical and laboratory measures and indicates the potential of IL-22 as an additional tool for assessment of activity in RA, particularly in patients with RF antibodies. IL-22 is associated with bone destructive disease.
Keywords: Interleukin-22, Rheumatoid arthritis, Disease activity, Disease activity score 28.