Quantitative studies of the specificity of anti-pneumococcal polysaccharide antibodies, Types III and VIII-V. Cross-reacting antibodies in rabbit antisera

Abstract

The specificity of the antigen-binding sites of high-titer cross-reacting antibodies of restricted heterogeneity present in the serum of two rabbits immunized respectively with Type III and Type VIII pneumococcal vaccine have been studied and compared quantitatively. Despite the fact that the two antibodies, anti-S3,8 and anti-S8,3 could be precipitated almost completely by either S3 or S8 alone, they could be distinguished easily from one another by the following procedures: (1) Selective precipitation of the homologous polysaccharide from mixtures of the two antigen excess using 14C-internally labeled S3 as one of the reactants, (2) inhibition of homologous and heterologous precipitation by cellobiuronate, the disaccharide unit responsible for the cross-reaction and (3) equilibrium dialysis against labeled homologous and heterologous oligosaccharide ligands.