Exploring The Relationship between FOXP3⁺ Regulatory T Cells, Eosinophilia, and Disease Severity in Chronic Rhinosinusitis with Nasal Polyps

INTRODUCTION: Chronic Rhinosinusitis (CRS) is a common condition causing a significant worldwide burden, affecting 5%-12% of the general population. The immunoregulatory mechanisms underlying eosinophilic and non-eosinophilic CRS with polyps (CRSwNP) remain incompletely understood, particularly with respect to regulatory T cells, FOXP3⁺. MATERIALS AND METHODS: Using immunohistochemistry, nasal polyp tissues from eosinophilic (ECRS) and non-eosinophilic (NECRS) CRSwNP patients were examined for FOXP3⁺ Treg expression, and symptoms and disease severity measures were obtained, including on quality of life. RESULTS: Comparative analysis along with clinical severity assessment did not demonstrate significant differences between eosinophilic and non-eosinophilic CRSwNP in FOXP3⁺ score (5.14 vs. 4.81, p=0.453), nasal polyp score (p=0.315), SNOT-22 (p=0.510), SST (p=0.295), or VAS (p=0.182), with small to medium effect sizes (Cohen’s d=0.25-0.50). Correlation analysis revealed no significant associations between FOXP3⁺ expression and clinical parameters, although SST showed a weak inverse association (ρ= –0.335, p=0.070). Significant correlations were observed between VAS and SNOT-22 (ρ= –0.549, p=0.0017) and between SNOT-22 and SST (ρ= –0.470, p=0.0088), indicating consistency between subjective and objective measures. CONCLUSION: These findings suggest that FOXP3⁺ regulatory T cell infiltration alone may not distinguish CRSwNP endotypes, underscoring the complexity of immune regulation beyond eosinophilic status. Larger, functionally focused studies are required to further elucidate the role of Tregs in CRSwNP.