ANTIGENICITY OF PNEUMOCOCCUS 353 



from Pneumococcus possessed a greater anti-opsonic action than 

 the deacetylated polysaccharide. The opsonic titer of normal hu- 

 man serum was practically nullified by the addition of the A carbo- 

 hydrate, while in immune serum the A carbohydrate brought about 

 a greater diminution in opsonic activity than did its derivatives. 

 The result was therefore a complete inhibition of the pneumococ- 

 cidal action of normal serum and a partial blocking of the same 

 action of specific immune serum. The inhibitory or antagonistic be- 

 havior of the carbohydrate fraction of Pneumococcus calls for 

 careful discrimination in the selection of the antigenic dosage of. 

 pneumococcal materials for the production of active immunity and 

 also for conducting serological reactions which have to do with the 

 immune state. 



Summary 



The substance of the material presented in this chapter may be 

 expressed as follows : The immunizing properties and type-specific 

 antigenic action of Pneumococcus and its derivatives are directly 

 proportional to the virulence of the culture employed and appear 

 to be the same whether the organism is in a living condition or ap- 

 propriately killed by heat or by formalin, the integrity of the 

 immunizing principle being better preserved in suspensions of heat- 

 killed than of formalinized pneumococci. Filtrates from fluid cul- 

 tures and watery or saline extracts of pneumococci, representing 

 as they do only a part of the antigenic components of the pneumo- 

 coccal cell, are more limited in immunizing properties than the en- 

 tire cell. Although specially prepared broth cultures may exhibit 

 a toxic action in animals, it does not necessarily follow that the in- 

 jection of the alleged toxins results in the production of pneumo- 

 coccal antitoxin. To be sure, some evidence of such a possibility 

 has been presented but at the present time it would be going be- 

 yond the facts to say that Pneumococcus contains or elaborates a 

 true toxin or that antitoxic processes are a recognized part of the 

 immunological mechanism against Pneumococcus. 



