Immunochemistry of pneumococcal types II, V, and VI. II. Inhibition tests in the type VI precipitating system.

Rebers, Paul A. (Rutgers University, New Brunswick, N. J.), Esther Hurwitz, and Michael Heidelberger. Immunochemistry of pneumococcal types II, V, and VI. II. Inhibition tests in the type VI precipitating system. J. Bacteriol. 82:920-926. 1961.-As in other immune systems involving polysaccharides, rabbit antibodies but not those engendered in the horse were found sensitive to degradation of type VI pneumococcal (Pn) polysaccharide (SVI), and were readily inhibited by fragments of SVI. Large amounts, 30 to 111 mumoles, of most sugars gave up to 15% inhibition, while sugar and polyol phosphates inhibited as much as 25%, with little relation to their presence or absence in SVI. The phosphate-free repeating unit of SVI was a good inhibitor, its phosphate monoester was better, and the "trimer" still better. The "trimer" precipitated most of the antibodies from horse anti-Pn VI.Although inhibition of precipitation of SVI anti-Pn horse sera could not be demonstrated with fragments of SVI, cross-reactions of antibodies in the horse sera could be inhibited. Precipitation of SII was inhibited by low concentrations of l-rhamnose, while even high concentrations of the other sugar components of SII and SVI were ineffective. Precipitation by guar gum was inhibited by galactose and alpha- and beta-methyl-galactopyranosides, also by rhamnose, although guar gum does not contain this sugar, while SVI, the antigenic determinant, does.