ANTIBODIES TO PNEUMOCOCCUS 371 



Pneumococcus — the soluble specific substance — was concerned in 

 the particulation of type-specific antibody in immune serum. 



Heidelberger, Goebel, and Avery (1925) 613 confirmed the par- 

 ticipation of the soluble specific substance in immunological reac- 

 tions and refined the methods for the isolation of the polysaccha- 

 ride. The purified substance from Type I Pneumococcus gave a 

 specific precipitin reaction with homologous Type I antipneumo- 

 coccic serum and could be detected in a dilution as great as 1 to 

 6,000,000. Similar refined preparations from Type II and Type 

 III pneumococci showed antigenic reactions of approximately the 

 same magnitude, and in the precipitin reaction exhibited strict 

 type-selectivity for the precipitins in homologous serum. The ob- 

 servations substantiated the view that the polysaccharides were 

 the actual specific antigenic substances of Pneumococcus. 



That the specific precipitinogen in Pneumococcus is evidently 

 a soluble carbohydrate was shown in a different manner by Schie- 

 mann and Casper (1927), 1228 who dissolved pneumococci in sodium 

 taurocholate, and found that the solutions gave type-specific pre- 

 cipitates with homologous immune serum. The authors rightly be- 

 lieved that the soluble carbohydrate obtained by lysis of the cocci 

 with the bile salt was the same as the type-specific polysaccharide 

 isolated and tested by Avery and Heidelberger. 



Later (1931), Avery and Goebel 45 proved that the type-speci- 

 ficity of the interaction of Pneumococcus and homologous immune 

 serum was due to the capsular polysaccharide and not to the pro- 

 tein of the cell. The serum of rabbits immunized with an artificial 

 antigen, prepared by combining a specific derivative of the cap- 

 sular polysaccharide of Type III Pneumococcus with globulin 

 from horse serum, was found to contain specific precipitins for 

 the Type III polysaccharide and, in addition, precipitins for horse 

 globulin. It was, however, the capsular polysaccharide that was 

 the determining factor in the specificity of the antigen as a whole. 

 Subsequently, Avery and Goebel 46 proved that the acetyl poly- 

 saccharide, besides being antigenic in the sense of being capable of 



