title: Upper airway defence mechanisms.
abstract: The nose is the airconditioner of the airways. Because normal breathing is through the nose, most airborne particles are filtered there; hence the nasal mucosa is the first line of defence against particles in the air. Pathogenic and non-pathogenic antigens continuously bombard the epithelium of the nasal airway. These antigens are mainly removed non-immunologically by the first defence layer of the mucosa, consisting of mucus, ciliated epithelial cells, glycoproteins/lysosymes. If the antigen passes this defence layer, specific and non-specific immunological defence mechanisms exist. The non-specific defence consists of phagocyting cells like neutrophils and macrophages and the complement activation. The specific defence mechanism (resulting in a specific immunological reaction in relation to a certain antigen) is formed by the antibodies, mainly secretory IgA and to a lesser extent IgG and immunocompetent cells in the nasal mucosa. Activation of the specific defence mechanisms may lead to inflammation which can be allergic. The intense co-operation of mechanical, aspecific and specific immunological defence results in a tightly controlled balance between a proper defence against pathogens and hypersensitivity. Failures in these defence mechanisms, or their co-operation, results in upper respiratory infection and/or allergy.
authors.affiliation: Dept. of Otorhinolaryngology, Erasmus University Medical Centre, Rotterdam, The Netherlands.
authors.forename: W J
authors.initials: WJ
authors.lastname: Fokkens
authors.forename: R A
authors.initials: RA
authors.lastname: Scheeren
mesh_terms: D001798:Blood Proteins / Q000502:physiology; D002648:Child; D006801:Humans; D007111:Immunity, Cellular; D018928:Immunity, Mucosal; D009079:Mucociliary Clearance / Q000502:physiology; D009093:Mucus / Q000502:physiology; D020545:Respiratory Mucosa / Q000503:physiopathology; D012140:Respiratory Tract Diseases / Q000276:immunology* / Q000517:prevention & control*
chemical_list: D001798:Blood Proteins