Skin colonization of Staphylococcus aureus harboring superantigen toxin genes and its correlation with serum IL-22 level in psoriasis patients

Psoriasis is a chronic debilitating skin disease with an estimated prevalence reaching 2% of the worldwide population. Psoriatic disease is driven by the interactions among innate and adaptive immune systems with structural components of the skin. Interleukin (IL)-22 mediates keratinocyte proliferation and epidermal hyperplasia, and changes in the structure of skin flora can play a role in the secretion of IL-22. The aim of this study was to correlate serum levels of IL-22 and Staphylococcus aureus toxins with disease activity in plaque psoriasis. The study group included 50 patients with mild, moderate, and severe psoriasis. The control group comprised 20 sex- and age-matched apparently healthy volunteers. IL-22 concentration was assessed in sera of patients and the control group by using the ELISA technique. The serum levels of IL-22 in patients were higher than in the control group, but the difference was statistically insignificant (P=0.413). Serum IL-22 levels were positively correlated with the Psoriasis Area and Severity Index (PASI) score of psoriasis patients (P=0.0003). The IL-22 serum levels in patients colonized with toxigenic strains of S. aureus were significantly higher than in patients colonized with non-toxigenic strains (P= 0.028). In conclusion, IL-22 plays a role in the pathogenesis of psoriasis, and its secretion can be triggered by the toxins produced by S. aureus colonizing the skin of patients.