beta-1,2-linked oligomannosides from Candida albicans bind to a 32-kilodalton macrophage membrane protein homologous to the mammalian lectin galectin-3

beta-1,2-linked oligomannoside residues are present, associated with mannan and a glycolipid, the phospholipomannan, at the Candida albicans cell wall surface. beta-1,2-linked oligomannoside residues act as adhesins for macro phages and stimulate these cells to undergo cytokine production. To charact erize the macrophage receptor involved in the recognition of C. albicans be ta-1,2-oligomannoside we used the J774 mouse cell line, which is devoid of the receptor specific for alpha-linked mannose residues. A series of experi ments based on affinity binding on either C. albicans yeast cells or beta-1 ,2-oligomannoside-conjugated bovine serum albumin (BSA) and subsequent disc losure with biotinylated conjugated BSA repeatedly led to the detection of a 32-kDa macrophage protein. An antiserum specific for this 32-kDa protein inhibited C. albicans binding to macrophages and was used to immunoprecipit ate the molecule. Two high-pressure liquid chromatography-purified peptides from the 32-kDa tryptic digest showed complete homology to galectin-3 (pre viously designated Mac-2 antigen), an endogenous lectin with pleiotropic fu nctions which is expressed in a wide variety of cell types with which C. al bicans interacts as a saprophyte or a parasite.