Isolation of type-specific antibody to streptococcus pyogenes by affinity chromatography.

Rabbit type-specific opsonic antibodies to type 1 and type 12 streptococci were isolated by affinity chromatography on immobilized phage-enzyme extract. They were tested by precipitation in gel, bactericidal test and radioimmunoassay. Only type-specific activities were demonstrated. These activities were distributed homogeneously according to avidity. No suggestion of opsonizing and precipitating activities being separable from each other was found. These highly purified rabbit antibodies were marked by radioiodination and used to titrate human anti-M antibodies by competition. These marked antibodies were also used for the study of type-specific antigenic determinants on streptococcal antigens.