Studies on the Antigenic Activity of Yeasts

In order to determine the determinant antigenic group of the mannan of Saccharomyces cerevisiae , a series of inhibition tests were carried out employing oligosaccharides which separated from the acetolyzate and the hydrolyzate of the mannan. Tetraose, Man α1→3 Man α1→2 Man α→2 Man 2 , corresponding to the structure of the longer branching moieties of the mannan showed the strongest inhibition, while the isomer, Man α1→6 Man α1→6 Man, corresponding to the core moiety, produced only one‐tenth the inhibition of the former. This provides evidence that the branching moieties of the mannan play important role in combining with antibody. The fact that the disaccharide, Man α→3, showed significantly stronger inhibition than those of the other disaccharides, Man α1→2 Man and Man α1→6 Man, indicates that the most important part of the determinant group of the mannan is α1→3 linked D‐mannose residue. The antigenic inactivity of the periodate‐oxidized mannan containing unoxidized mannose residues indicates that the presence of 3‐O‐substituted‐D‐mannose residues adjacent to the D‐mannose residues and joined with α1→d2 linkages, are essential to fit the combining site of the antibody.