Immunolocalization of Dendritic Cells and Pattern Recognition Receptors in Chronic Rhinosinusitis

Abstract

Background Dendritic cell (DC) activation and antigen presentation to T cells are critical to innate and adaptive immunity. Toll-like receptors (TLRs) are known to bind pathogen-associated molecular patterns in addition to sinonasally secreted surfactant proteins (SP) such as SP-A and SP-D. TLR binding is known to activate DCs. Based on these observations, we sought to establish the presence, in sinonasal mucosa, of DC and the pattern recognition receptors (PRRs), CD14, TLR2, and TLR4. Methods Sinonasal biopsy specimens were taken from patients with eosinophilic nonatopic nasal polyposis (n = 4), allergic fungal sinusitis (n = 1), and nondiseased patients undergoing cerebrospinal fluid leak repair or pituitary tumor resection (n = 2). Tissue samples were stained immunohistochemically for PRR (CD14, TLR2, and TLR4), mature DC marker (CD208), iDC marker (CD209), or isotype controls. Results Immature and mature DC were immunolocalized to the subepithelial stroma and ciliated epithelial surface, respectively. Diffuse staining of CD14 was observed throughout the stroma with additional staining in the ciliated epithelium. The TLR markers showed no staining in the ciliated epithelium. TLR2 primarily localized in stroma immediately deep to the ciliated epithelial surface. TLR4 immunolocalized to submucosal seromucinous gland ductal epithelium. Data from nondiseased patients were mixed, with one patient showing minimal staining of any of the tested cellular markers. Conclusion This study indicates progressive DC activation and emigration of mature antigen-presenting cells from the epithelial surfaces of sinonasal mucosa. The presence of TLR known to bind SP-A and SP-D suggests a link between SP expression and immune response in sinonasal mucosa.