Th17/Treg Imbalance Reveals Local–Systemic Immune Dissociation in Nasopharyngeal Inflammation and Its Association with Endoscopic Severity

Background and Objectives: Nasopharyngeal inflammation is difficult to assess using systemic biomarkers alone, and the diagnostic value of mucosal immune profiling remains unclear. Th17/Treg imbalance is implicated in chronic mucosal inflammation, but its local–systemic relationship in the nasopharynx has not been defined. This study aimed to characterize mucosal and peripheral immune profiles in nasopharyngeal inflammation and to evaluate their association with endoscopic severity. Materials and Methods: Thirty-eight patients with nasopharyngeal inflammation underwent endoscopic evaluation and immune profiling of both mucosal samples and peripheral blood. Th17 and Treg cell proportions were quantified by flow cytometry. A subset of 20 patients was reassessed after standardized epipharyngeal abrasive therapy (EAT) to evaluate systemic immune changes. Results: Mucosal Th17/Treg ratios were significantly higher than peripheral ratios, indicating a distinct local immune activation pattern. Mucosal Th17/Treg ratios were significantly correlated with endoscopic severity scores, whereas peripheral ratios showed no such association. Following EAT, peripheral Th17 levels decreased significantly (p = 0.031), whereas the Th17/Treg ratio did not change significantly. Mucosal Th17/Treg ratios also did not change significantly. Conclusions: Nasopharyngeal inflammation is characterized by an elevated mucosal Th17/Treg ratio that is not reflected in peripheral immune markers, suggesting compartment-specific differences between mucosal and peripheral immune responses. Mucosal Th17/Treg ratio was associated with endoscopic severity, whereas peripheral Th17 reduction was observed after EAT. Direct mucosal immune assessment may be important for accurate evaluation of local inflammatory activity and endoscopic disease severity.