Investigations on some antigenic relationships between different human, mammalian and avian Chlamydia strains.

: Serological investigations were performed in order to establish the antigenic relationships between three Chlamydia strains: T44(subgroup A), T13 and Q18 (subgroup B). By using monospecific mouse immune sera a certain degree of antigenical relationships was made evident and the strains could be typed by microagglutination and microimmlnofluorescence reactions. Similar results were obtained by seroneutralization with hyperimmune sera prepared in the rooster. Complement fixation proved to be a group-specific reaction unable to reveal significant differences between the strains studied, not even with monospecific mouse sera. The antigenic relationships established between strains T44 (trachoma) and T13 (psittacosis) suggest the existence features common to subgroup A and B Chlamudia strains. The importance of typing Chlamudia strains with a view to specific prophylaxis is emphasized.