Specificity of monoclonal antibodies against group B streptococcus type II and inhibition of their binding by human secretions.

Mouse monoclonal antibodies against the type-specific polysaccharide antigen of type II group B Streptococcus may be divided into two general groups based on their antigen-binding properties. One group of antibodies binds to both intact and desialylated type II antigen and the binding can be inhibited by beta-galactopyranosides. The second group of antibodies react only with intact type II polysaccharide and are not inhibited by beta-galactopyranosides. The binding of antibodies of the first group can also be inhibited by carbohydrate components of normal human secretions that share structural similarities with the type II polysaccharide. The binding of antibodies of one specificity precluded the binding of antibodies of the other specificity, apparently by competing for binding sites within a combining area that includes both determinants.