Reduced Numbers of Blood Dendritic Cell Antigen 3 Positive Dendritic Cells in the Nasal Mucosa Contribute to Severe Inflammation in Patients with Allergic Rhinitis and Chronic Rhinosinusitis

Background Dendritic cells (DCs) are antigen-presenting cells that play a critical role in airway diseases by initiating and regulating immune responses. DCs are classified into plasmacytoid DCs (pDCs) and conventional DCs (cDCs), with the cDC lineage further divided into cDC1 and cDC2 subsets. Each subset exhibits distinct functions in immune regulation and disease pathogenesis. Thus, analyzing DC subsets is crucial for understanding the pathogenesis of airway diseases with diverse endotypes. Objective Allergic rhinitis (AR) and chronic rhinosinusitis (CRS), further divided into eosinophilic CRS (ECRS) and non-eosinophilic CRS (NECRS), are typical upper airway diseases with diverse endotypes. AR and CRS often occur simultaneously, and their severity tends to increase when they are comorbid. To understand the endotypes of AR and CRS, we classified the presence or absence of AR and CRS, analyzed the changes in DC subsets in the nasal mucosa, and compared these results with clinical features. Methods Nasal polyp tissues and ethmoid mucosa were collected from 42 patients who underwent endoscopic sinus surgery. DC were analyzed by flow cytometry to detect the expression of blood DC antigen (BDCA)-1, BDCA-2, and BDCA-3. Results BDCA-3 + cDC levels were significantly reduced in patients with both AR and CRS, compared to those with AR alone or CRS alone. This reduction was especially prominent in patients with ECRS, polysensitization, and total serum IgE ≥ 200 IU/mL. BDCA-3 + cDC levels were also inversely correlated with preoperative computed tomography scores and serum eosinophil and immunoglobulin E levels. Conclusion BDCA-3 + cDC levels may be involved in mucosal immune regulation and are associated with increased disease burden in patients with comorbid AR and ECRS.