Beta-glucans with 1,2 and 1,6 glycosidic linkages are the major structural components of yeast and fungal cell walls and are active pharmacologic agents in animal host defense systems. A purification scheme has been devised for isolating a unit ligand yeast heptaglucoside recognized by human monocyte beta-glucan receptors and gene-screening a human monocyte cDNA library with an anti-idiotype that is complementary to a monocyte Beta-glucan receptor has resulted in the isolation of three recombinant phages with immuno-specific cDNAs. The studies in this proposal deal with further characterizations of yeast carbohydrate ligands and the human receptors which recognize them. Research is first directed at scale-up production of the yeast heptaglucoside for subsequent determination of its complete primary structure, second, at sequencing the three purified monocyte cDNAs to a beta-glucan receptor protein and preparing antibodies to it with recombinant monocyte fusion products, third, at determining the amino acid sequences of isolated U937 cell proteins that bind yeast beta- glucans and preparing antibodies to these proteins, and fourth, at determining the cellular distribution of beta-glucan receptors on resting and activated cells with radiolabeled soluble yeast ligands and receptor- specific probes. Long-term objectives are first to computer-generate structural models of the defined heptaglucoside for formulating chemical reactions of synthetic active analogs, second, to study the regulation and biosynthesis of this monocyte beta-glucan receptor protein, third, to determine if monocyte beta-glucan receptors are composed of multiple structural subunits in a fashion analogous to those on U937 cells, and, fourth, to study transcriptional and post-transcriptional mechanisms involved in the synthesis of beta-glucan receptors by monocytes and by other cell types that express these receptors. The characterization of these receptors and their ligand specificities for discrete structures in microbial cell walls would define a major cell effector system that is operative in the absence of adaptive immunity. This system provides a physiologic mechanism for general health maintenance which may only become apparent in the debilitated host. Adjuvant usage of yeast glucans or their active analogs for patients with acute or chronic disease offers a therapeutic modality for mobilizing natural defense molecules from human reserves and providing a more improved and rapid recovery.
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