ANTI-IMMUNOGLOBULINS IN EXPERIMENTAL STREPTOCOCCAL IMMUNIZATION; RELATION TO BACTERIAL GROWTH CONDITIONS AND Fc-RECEPTORS

Heat-killed group A streptococci of types M12 and M22 were used for intravenous immunization of 60 rabbits. Presence of Fc-receptors binding monomeric IgG in M22 and their absence in M12 has been demonstrated previously. The strains were cultured in either Todd-Hewitt broth supplemented with 10% horse serum (TH-H) or in IsoVitaleX, a synthetic medium, supplemented with 10% autologous rabbit serum (IV-R). A mortality rate of 38% was noted in the first-mentioned group whereas no mortality was observed in the second group. Sera were examined for agglutination of red blood cells coated with either human or rabbit IgG. Antisera to strains cultured in TH-H regularly displayed anti-IgG antibodies reacting with human as well as rabbit IgG; anti-rabbit IgG titres of anti-M22 sera were significantly higher than those of anti-M12 sera. Antisera to strains grown in IV-R displayed high levels of antibodies reacting with human but not with rabbit IgG. The levels of anti-human IgG did not differ between anti-M12 and anti-M22 sera.