INTERACTION OF MURINE MACROPHAGE-MEMBRANE PROTEINS WITH COMPONENTS OFTHE PATHOGENIC FUNGUS HISTOPLASMA-CAPSULATUM

The interaction of macrophage-membrane proteins and histoplasmin, a cr ude antigen of the pathogenic fungus Histoplasma capsulatum, was studi ed using murine peritoneal macrophages. Membrane proteins were purifie d via membrane attachment to polycationic beads and solubilized in Tri s-HCl/SDS/DTT/ glycerol for protein extraction; afterwards they were a dsorbed or not with H. capsulatum yeast or lectin binding-enriched by affinity chromatography. Membrane proteins and histoplasmin interactio ns were detected by ELISA and immunoblotting assays using anti-H. caps ulatum human or mouse serum and biotinylated goat anti-human or anti-m ouse IgG/streptavidin-peroxidase system to reveal the interaction. Res ults indicate that macrophage-membrane proteins and histoplasmin compo nents interact in a dose-dependent reaction, and adsorption of macroph age-membrane proteins by yeast cells induces a critical decrease in th e interaction. Macrophage-membrane glycoproteins with terminal D-galac tosyl residues, purified by chromatography with Abrus precatorius lect in, bound to histoplasmin; and two bands of 68 kD and 180 kD of transf erred membrane protein samples interacted with histoplasmin components , as revealed by immunoblot assays. Specificity for beta-galactoside r esidues on the macrophage-membrane was confirmed by galactose inhibiti on of the interaction between macrophage-membrane proteins and histopl asmin components, in competitive ELISA using sugars, as well as by enz ymatic cleavage of the galactoside residues.