ANTIBODIES TO PNEUMOCOCCUS 377 



groups in the immune protein may determine its specific capacity 

 to react with the polysaccharide of the homologous type. 



In the carbohydrate of Type I Pneumococcus the authors be- 

 lieved, on the basis of the experimental evidence, that the carboxyl 

 groups of the polysaccharide are the dominant groups which in- 

 teract to form the immune precipitate. The questions whether the 

 carboxyl groups of the polysaccharide actually combine with the 

 amino groups of the antibody protein and whether the formation 

 of an insoluble precipitate involves further chemical change in the 

 protein molecule, such as specific denaturation, cannot be an- 

 swered at present. However, Chow and Goebel concluded : 



The specificity of this reaction is determined by the stereochemical 

 relationship of the dominant polar groups in the reacting molecules, 

 whether they be antigen or antibody. If the spatial pattern of the polar 

 groups of both antigen and antibody is of exactly the correct order, 

 then union occurs. If, however, this relationship is disturbed by arti- 

 ficial means, as has been experimentally demonstrated by covering the 

 dominant polar group of either polysaccharide or antibody with a 

 chemical radical, the pattern is destroyed and union between them is 

 either greatly modified or fails to take place. When the original consti- 

 tution of the reacting substances is restored, however, serological speci- 

 ficity is regained. 



CORRELATION OF PRECIPITINS WITH OTHER ANTIBODIES 



Many observations have been made on the quantitative relation- 

 ships existing between precipitins and other specific antibodies in 

 antipneumococcic serum. The discovery that the capsular poly- 

 saccharide functions as the precipitinogen in the reaction, and the 

 development of methods for evaluating the strength of antigen 

 and antibody, have made possible more exact determination of the 

 amount of precipitin in a given serum in relation to the content 

 of other immune substances. Friedlander, Sobotka, and Banzhaf 

 (1928) 493 estimated, under known conditions, the precipitin in- 

 dices of a number of monovalent and polyvalent antipneumococcic 



