Immunological and physiological responses of nasal mucosa and the role in nasal pathology

Abstract

Nasal mucosa is equipped with several physiological functions such as mucociliary transportation of invading pathogens as well as allergens and nonspecific host-defending function with lysozyme and glycoconjugates. Furthermore, the mucosal immune system protects nasal mucosa mainly with secretory IgA. Secretory IgA cannot activate complements and kill bacteria, but can inhibit bacteria by adhering to epithelial cells by agglutination and coupling the receptors. Nasal secretions contain a high concentration of secretory IgA, which is much higher than the concentrations of serum type IgA, IgG, and IgM. In chronic sinusitis, the production of those immunoglobulins is increased, and the concentrations are higher than those in healthy subjects. However, the pathogen-specific antibody activities of those immunoglobulins are decreased in chronic sinusitis, suggesting that the local immune system is damaged by chronic inflammation. Those findings indicate that activation of the mucosal immune system might be effective for preventing nasal as well as sinus infections. Animal experiments using mice demonstrated that intranasal immunization is more effective than oral or systemic immunization to induce antigen-specific immune responses in the nose. The results suggest that nasal vaccination might be a useful and promising strategy for preventing upper respiratory infections including nasal infectious diseases.