LUNG SURFACTANT PROTEIN-A AND PROTEIN-D CAN INHIBIT SPECIFIC IGE BINDING TO THE ALLERGENS OF ASPERGILLUS-FUMIGATUS AND BLOCK ALLERGEN-INDUCED HISTAMINE-RELEASE FROM HUMAN BASOPHILS

Aspergillus fumigatus is an opportunistic fungal pathogen which, in th e immunocompetent host, causes allergic disorders such as allergic rhi nitis, allergic sinusitis, hypersensitivity pneumonitis, and allergic bronchopulmonary Aspergillosis (ABPA). In the present study, the inter action of 3-week culture filtrate (3wcf) allergens and various purifie d glycosylated and non-glycosylated allergens of A. fumigatus with lun g surfactant proteins, SP-A and SP-D, was investigated. Purified SP-A and SP-D, isolated from human bronchoalveolar lavage fluid, bound to t he 3wcf allergens and purified allergens, gp55 and gp45, in a carbohyd rate-specific and calcium-dependent manner. Both SP-A and SP-D did not bind to deglycosylated allergens, suggesting that the ability of SP-A and SP-D to bind certain allergens is mediated through their carbohyd rate recognition domains, interacting with the carbohydrate residues o n the allergen. Both SP-A and SP-D could inhibit the ability of allerg en-specific IEE from Aspergillosis patients to bind these allergens, s uggesting that SP-A and SP-D may be involved in the modulation of alle rgic sensitization and/or development of allergic reactions. The view that SP-A and SP-D play a protective role against airborne allergens i s further supported by the demonstration of their ability to inhibit A . fumigatus allergen-induced histamine release from allergic patients' basophils.