The presence of CD209 expressing dendritic cells correlates with biofilm positivity in chronic rhinosinusitis with nasal polyposis.

Biofilm-positive cases of chronic rhinosinusitis with nasal polyposis (CRSwNP) may form a separate clinical entity, which is characterized by high recurrence rates and resistance against different therapeutic strategies. This can be explained by a special immunologic phenotype. Biofilm existence has been supposed to correlate with increased amount of dendritic cells that are responsible for antigen presentation in CRSwNP. A total of 20 patients with CRSwNP undergoing endoscopic sinus surgery (ESS) were analyzed. The negative control group consisted of ten patients undergoing septoplasty without CRSwNP. Three series of individual nasal polyps and control specimens were processed to hematoxylin-eosin (HE) and Gram staining and to CD209-specific immunofluorescent assay, respectively. Biofilm was detected in 13 of 20 patients (65 %) with CRSwNP and in none of the ten negative controls. The subepithelial layer of biofilm-positive nasal polyps displayed a statistically significant (p < 0.001) increase in the numbers of CD209-expressing dendritic cells compared to biofilm-negative specimens. It was found that biofilm detectability showed strong correlation to the architecture of respiratory mucosa and to the dominant inflammatory cell type of the subepithelial layer. Persisting bacterial biofilms may affect the type of antigen presentation and consecutive immune reactions in the subepithelial layer of nasal mucosa. This phenomenon may result in different inflammatory pathways with specific cytokine profile compared to biofilm-negative cases. Co-existence of bacterial biofilms and dominant pattern of dendritic cells suggest a biofilm-associated immunologic phenotype in CRSwNP. This can explain the mucosal changes, functional disorders and therapy resistance featuring CRSwNP.