I. Pneumococcal Polysaccharide as Inducer and Elicitor of Delayed P~eactivity in Guinea Pigs By

For example, in the test devised by Tiller and Francis (1) for patients with lobar pneumonia, the intradermal injection of purified pneumococcal polysaccharide derived from the infecting type of organism gave rise to reactions of the immediate type, although the pneumococcus is known to induce delayed reactivity to its protein constituents (1, 2). In work with blood group substances, Holborow and Loewi (3) found antibodies to be produced against the sugar components, while delayed reactivity, which was also seen, was attributed to the peptide moiety of these substances. Similar conclusions were reached using chondromucoprotein as antigen (4). Jankovic and Waksman (5) also concluded that delayed hypersensitivity induced by the saccharide-peptides of human erythrocytes may have been in part directed against the peptide structure. Barker and coworkers (6) with polysaccharide from Trichophyton concluded that it participated in antibody-mediated reactions, the protein of the organism in delayed ones. In 1963 it was demonstrated that monoand disaccharides coupled to protein carrier induced delayed reactivity elicitable by the same hapten attached to different carriers, although homologous conjugates were best for the purpose (7). Several reports describe the induction of delayed reactivity to polysaccharides, while presumably obviating the possible role of associated peptides. Thus, Knight et al. (8-10) described the induction of delayed reactivity in guinea pigs to polysaccharides of Histoplasma capsulatum and Blastomyces dermatitidis by sensitization with whole fungi and testing with appropriate polysaccharide preparations, but these contained 4-5% nitrogen. Freund et al. (11) induced aspermatogenesis in guinea pigs with testicular extract