Purification of the human alveolar macrophage mannose receptor

We report here the first isolation of a mannose receptor from human lung, and identify the alveolar macrophage as the cell of origin. The receptor was purified from detergent-solubilized lung tissue by absorption to mannose- and fucose-Sepharose, and elution with EDTA. The eluted protein had a molecular weight of 175 kD. Maximum binding of 125I-mannan-2 to the isolated receptor occurred at pH 7.5. Binding was inhibited by 40 micrograms/ml mannan (75%); 200 mM mannose (89%); and 200 mM fucose (93%). Galactose (200 mM) had no effect. Polyclonal antibodies raised against the purified receptor reacted with the purified 175 kD protein and a 175 kD protein from detergent extracts of human alveolar macrophages by immunoblot analysis. The antibody immunoprecipitated a 175 kD protein from solubilized 125I-labeled human alveolar macrophage membranes. These studies indicate that the 175 kD protein purified from human lung is the cell surface alveolar macrophage mannose receptor.