Cell antigens recognized by rabbit antibodies specific for oligomannosyl determinants

Rabbit antibodies to cell wall mannans of various microbial strains and their mutants were found to be cross-reactive to cell carbohydrates of mammalian sperm and 4-6-days-old blastocysts. Immunochemical studies indicate that oligomers of alpha1 yields to 2, alpha1 yields to 3, alpha1 yields to 6, and probably also alpha yields to 4 linked mannose residues of sperm carbohydrates are available for antibody binding. At least 80 percent of binding activity of a yeast mannan antibody to sperm can be effectively inhibited by specific haptens or digestion with exo-alpha-D-mannosidase, an enzyme activity highest in testicular tissue. In order to determine the role of this enzyme in the metabolism of the cross-reactive mannan antigens of sperm, the relative amount of a specific alpha-linked oligomannosyl determinant of bovine sperm from homozygous normals was compared to that of hetero-zygous carriers of alpha-mannosidase deficiency. Extensive cross-reactivity between the microbial and mammalian oligomannosyl determinants suggest that these are conserved structures in cell carbohydrates, although the organization of these units in the microbial cell wall lipopolysaccharide has very little similarity to the carbohydrate moieties of mammalian glycoproteins.