The Protective Role of IL-17 and IL-22 in COVID-19 Infection

Background: The development of a cytokine storm in Coronavirus Disease 2019 (COVID-19) infection can make the disease fatal. We hypothesize that this excessive cytokine production impairs mucosal healing. IL-17 and IL-22 are cytokines that play a key role in protecting and regenerating mucosal tissues. IL-17 and IL-22 support each other, and the imbalance between them plays a role in the pathogenesis of many rheumatologic diseases. Objective: To investigate whether COVID-19 severity is related to IL17, IL-22, and the IL-17/IL-22 ratio. Methods: The study was planned prospectively and included 69 patients with active COVID-19 infection. Three groups were created: patients with upper respiratory tract infection, pneumonia, and cytokine storm. Blood samples were taken from the patients upon their first admission and serum levels of IL-17 and IL-22 were measured using the enzyme-linked immunosorbent assay (ELISA). We assessed the relationship between IL17, IL22, IL17/ IL22 ratio, clinical and lung involvement by comparing them with the healthy group. Results: The levels of IL-17 were significantly higher in COVID-19 patients with upper respiratory tract infection compared to the control group (p=0.027). p =0.027). IL17/IL-22 ratio significantly increased in patients with cytokine storm compared to the healthy controls (p=0.027). p =0.027). Serum levels of IL-22 were negatively correlated with the CO-RADS score (r=-0.31, p =0.004), while IL-17/IL-22 ratio was positively correlated with the CO-RADS score (r=0.29, p =0.008). Conclusion: Levels of IL-17, IL-22, and IL-17/IL-22 may provide valuable into the of COVID-19.