A general understanding of the interaction of (monoclonal) antibodies with their homologous saccharides is important in order to a) gain an insight into the immunogenicity of oligo- and polysaccharides, and b) gain insights into the general nature of the interaction of proteins (including e.g. receptors, enzymes) with saccharide haptens (it has been shown that enzymes show common hapten-binding idiotypi with anti-hapten antibodies: Strickland et al. J. Immunol. 34, 1053, 1985). Of the three projects in the Section, two (A and B) are intimately tied to the above approach, while the third (C) is associated with it also: A. Study of the molecular interaction of monoclonal antibodies with polysaccharide antigens. B. The preparation and characterization of immunodiagnostic antibodies to saccharide determinants occurring on glycoproteins (GP) and glycolipids (GL). C. Chemistry of the antigens of the pathogenic fungus Cryptococcus neoformans, and their interaction with antibodies.