CHAPTER X 

 ANTIGENICITY OF PNEUMOCOCCUS 



The immunizing properties of Pneumococcus and of its compo- 

 nents and derivatives; factors which operate in establishing the im- 

 mune state; and the response of different animals to the antigenic 

 action of members of this bacterial species and their constituents. 



IN Chapter VIII the antigenic properties of the chemical con- 

 stituents of Pneumococcus were described only in a general way 

 in order to illustrate the similarities and dissimilarities of the pro- 

 tein and carbohydrate preparations which have been advanced as 

 representing the active substances native to the cell, and to empha- 

 size the dependence of immunological behavior on chemical consti- 

 tution. No attempt was made to give any systematic account of 

 the various antibodies or immune effects which the proteins and 

 polysaccharides call forth, or to compare and correlate the action 

 of the cellular fractions with that of the intact bacterial body. 



Antigenic Spectrum 



The antigenic spectrum of Pneumococcus can be resolved into 

 its dominant bands in several ways. Taking the whole, living, fully 

 virulent cell as the norm, its immunological action can be analyzed 

 through the stimuli provided by its separate constituents or de- 

 rivatives. There enter into the analysis the chemical structure of 

 the several components of the cell, the question of their mass, and 

 the route and spacing of their administration. 



The spectral bands — or less definitely, zones or regions — ap- 

 pearing after the introduction of pneumococcal materials into the 

 animal body, are represented by agglutinins, precipitins, bacteri- 

 cides, tropins or opsonins — conceivably the alleged antitoxins — 

 the complement-fixing and protective antibodies, and such manifes- 



