Increased IL-5, IL-33, and ST2 expression in pediatric adenoid hypertrophy associated with allergic rhinitis: Immunohistochemical and systemic evidence.

INTRODUCTION: Adenoid hypertrophy (AH) is a common paediatric disorder that may be worsened by allergic rhinitis (AR), contributing to persistent symptoms and postoperative recurrence. The immunologic mechanisms underlying allergic AH remain incompletely understood. This study assessed IL-5, IL-33, and ST2 expression in adenoid tissues of children with AH and evaluated the influence of concomitant AR on tissue and systemic inflammatory responses. METHODS: This study included 120 children undergoing adenoidectomy: 60 with AH alone and 60 with AH plus AR. Immunohistochemical staining was performed to assess tissue IL-5, IL-33, and ST2 expression using integrated optical density. Serum IL-4, IL-33, and IFN-γ levels were measured by ELISA, and total IgE and blood eosinophil fractions were also evaluated. Correlations between tissue and systemic inflammatory markers were analysed. RESULTS: Compared with the AH-only group, children with AH plus AR showed significantly higher tissue expression of IL-5, IL-33, and ST2. Serum IL-4, serum IL-33, total IgE, and eosinophil fractions were also significantly increased, whereas IFN-γ levels were reduced. Tissue IL-5 expression correlated positively with serum total IgE, eosinophils, IL-4, and IL-33, and negatively with IFN-γ. CONCLUSION: Children with AH and AR showed higher tissue expression of IL-5, IL-33, and ST2, together with differences in systemic allergic inflammatory markers. These findings support an association between AR and increased IL-5, IL-33, and ST2 expression in adenoid tissue. Further cellular, functional, and longitudinal studies are needed.