Evaluation of Th17 Cells, CD4+ T Cells, IL-17 and IL-22 in Streptococcus Pyogenes-Associated Psoriasis: An Integrated Immunological Study

Abstract

Background: Psoriasis affects 2 to 3% of adults worldwide. Once primarily associated with older age and the male sex, emerging data indicate a U-shaped psoriasis prevalence curve. Th17 cells produce IL-17 and IL-22, which drive keratinocyte activation and inflammation, respectively. Objective: The current research aims to examine the correlation between S. pyogenes infection and Th17-mediated immune responses in psoriasis patients by assessing circulating Th17 and CD4+ T-cell populations and serum levels of IL-17 and IL-22. Methods: A case-control study is proposed involving patients with clinically diagnosed psoriasis and apparently healthy controls. Clinical severity was assessed using the Psoriasis Area and Severity Index (PASI). Evidence of S. pyogenes infection was determined using throat swab culture and/or species-specific PCR, with antistreptolysin O (ASO) antibody measurement considered as an additional marker of recent streptococcal exposure. Peripheral blood was analyzed by flow cytometry for CD4+ and Th17 cells, while serum IL-17 and IL-22 were quantified by ELISA. Associations between streptococcal status, immune biomarkers, and psoriasis severity were evaluated using correlation, regression, and ROC analyses. Results: Previous Iraqi data demonstrated significantly higher serum IL-17 concentrations in psoriasis patients than controls and significantly lower CD4+ levels. An independent Iraqi study involving 75 psoriasis patients and 75 controls also reported significantly increased serum IL-17 and IL-22, with IL-22 values of 42.23 ± 0.95 pg/mL in patients versus 18.07 ± 0.32 pg/mL in controls. Conclusion: Integration of environmental factors and microbial co-factors must be incorporated into cellular and cytokine immune response profiles in order to better understand psoriasis.