ANTIBODY RESPONSE TO INFECTIONS WITH TYPE II AND THE RELATED TYPE V PNEUMOCOCCUS 1

Abstract

Cross agglutinations of freshly isolated strains of types II and V (Cooper, IIa, Avery) pneumococci in antipneumococcus horse antisera were observed frequently and, in some instances, in dilutions high enough to cause confusion in routine type determinations. Homologous type-specific agglu tinins and mouse protective antibodies were fairly con stant in patients with type II or V pneumococcus lobar pneumonia, who recovered. Fatal cases with either type failed to develop antibodies. Cross immunity was observed, but it was infrequent, low-grade, and could be demonstrated by mouse protection only. Where cross immunity occurred, only the organism recovered from the sputum was (absorption exps.) antigenically active. Unlike type III, when II or V pneumococci were re covered along with other organisms, the latter, according to resulting antibody formation, usually proved to be incidental, and types II or V were the significant in vaders.