CHAPTER XI 

 ANTIBODIES TO PNEUMOCOCCUS 



The nature of the immune substances appearing after the injec- 

 tion of Pneumococcus, its constituents, or products into the animal 

 body ; the detection and estimation of specific antibodies in im- 

 mune serum; with a brief discussion of the factors which operate 

 in establishing immunity to Pneumococcus. 



The introduction into animals of pneumococci, their deriva- 

 tives, or their several metabolic products generates a variety 

 of antagonistic substances which may serve to protect the animal 

 against subsequent infection with virulent members of this bac- 

 terial species. In the present chapter there will be discussed the 

 substances to be found in the circulating blood after active immu- 

 nization and analogous substances normally present in animals, as 

 well as changes in the somatic cells contributing to the immune 

 state induced by parenteral injection of pneumococcal materials. 

 The manifestations of the physiological functions aroused by 

 the administration to animals of different species of pneumococci 

 in one form or another are many and varied. Furthermore, the 

 substances evolved in the immune processes are so closely related 

 and so intimately mingled in immune serum that a discussion of 

 any one of the specific substances necessarily involves that of other 

 associated antibodies. However, in reviewing the investigations of 

 earlier workers, one finds that the various immunological effects 

 were discovered one by one, until the mosaic of pneumococcal im- 

 munity — still incomplete, to be sure — has assumed a definite pat- 

 tern which can now be recognized by improved serological and 

 biochemical methods. 



Agglutinins 



The first tangible effect referable to an altered bodily state fol- 

 lowing the injection of pneumococci was that of agglutinin for- 



