Humoral mucosal immunity in allergic rhinitis

BACKGROUND: Mucosa-immunologic aspects are gaining an increasing awareness in the pathophysiology of type I allergies. Humoral mucosal immune responses are dominated by secretory IgA, but there is evidence for a relevant role of IgG in nasal mucosa-associated lymphoid tissue. OBJECTIVE: was to measure allergen-specific immunoglobulins (IgA and IgG) in nasal secretions as an expression of a humoral mucosal immune response in allergic rhinitis. For tissue eosinophilia we studied nasal Eosinophilic Cationic Protein (ECP) and for mast cell activation nasal tryptase. METHODS: Nasal secretions of 40 patients suffering from allergic rhinitis were analyzed for allergen-specific IgA, IgG, and IgE, and for ECP and tryptase. Patients were highly sensitized against the major allergens of house dust mites, timothy, and birch pollen. 43 non-atopic individuals served as controls. In order to study possible effects of the actual pollen season on the studied parameter we secondly compared patients allergic to seasonal allergens co- (n = 28) and extra-seasonally (n = 41). In order to determine a possible influence of allergen-specific IgA in eosinophilic degranulation we additionally studied 5 patients after nasal allergen challenge. RESULTS: In allergic rhinitis we found significantly increased levels of allergen-specific immunoglobulins of all studied subclasses and allergens in nasal secretions. Comparison of nasal ECP and tryptase showed significantly increased concentrations in allergic individuals as well. Co-seasonally we found elevated allergen-specific IgE, ECP, and tryptase but lower concentrations of allergen-specific IgA and IgG. There was no association between late phase eosinophilia and IgA concentrations after local allergen challenge. CONCLUSIONS: The occurrence of allergen-specific immunoglobulins in nasal secretions is interpreted as a local humoral mucosal immune response. The physiologic role of local allergen-specific immunoglobulins is not clear to date. Involvement in degranulation of eosinophils or mast cells, like suggested before, seems unlikely.