The Measurement of Type- and Nontype-Specific Group A Hemolytic Streptococcal Antibody with an Hemagglutination Technique

Summary 1.Tannic acid modified red cells were sensitized with semipurified M protein preparations of group A hemolytic streptococci. The sensitizing antigens in addition to M protein, contained nontype-specific protein which interfered with the measurement of type-specific antibody in rabbit and human sera. 2.Serologic type-specificity was attained by incubation of the test sera with either crude or semipurified antigens from heterologous types. The use of homologous as well as heterologous semipure and crude antigens as inhibitors demonstrated that multiple reactions in human sera reflected the presence of different type-specific antibodies. 3.Serologic type-specificity was shown to correlate with biologic type-specificity.