Immunochemical studies of type IV and two group-like (Z) carbohydrate antigens of minute streptococci

Analysis of purified fractions of formamide extracts of Z₄IV and 8650 (Z₅) bacteria gave as composition rhamnose, glucose, galactose and N-acetyl-glucosamine in molar ratio’s for Z₄ antigen 9:0:2:5, for type IV antigen 4:4:4:1 and for Z₅ antigen 8:2:2:3. In contradistinction with other polysaccharide type antigens of minute streptococci all type IV reactivity was recovered from the buffer eluate of a DEAE cellulose column. The Z₅ antigen was present in both the water and the buffer eluate. Precipitin and inhibition reactions indicate that the serological reactions between both strains are cross reactions based on the presence of galactose in the determinant groups of type IV, group Z₄ and group Z₅ antigens. Inhibition reactions also suggest a role of β-galactosyl-glucose as immunodominant group of the Z₅ determinant. Partial acid hydrolysis of type IV antigen yielded four oligosaccharides. Analyses and inhibition reactions show that probably both trisaccharides β-galactosyl-glucosyl-galactose and β-galactosyl-glucosyl-rhamnose are determinant groups of the type IV antigen.