ANTIBODIES TO PNEUMOCOCCUS 423 



versely, Type II but not Type I or Type III antipneumococcic se- 

 rum reacted with yeast carbohydrate antigen but not to the degree 

 observed in the case of antiyeast serum and pneumococcal carbo- 

 hydrate. The action of different samples of antiyeast serum of 

 equal potency as to reactivity with yeast antigen varied greatly 

 when tested against pneumococcal antigen. 



Summary 



The substance of this chapter may be recapitulated as follows : 

 The introduction into the bodies of animals of suitable species of 

 pneumococci and some of their natural components augments or 

 brings into being an array of specific immune substances that serve 

 to protect the animal against the invading cocci and that can be 

 demonstrated by appropriate serological and other immunological 

 reactions. The immune substances thus evoked comprise agglu- 

 tinins, precipitins, opsonins or tropins, and complement-fixing and 

 protective antibodies. 



Agglutinins, arising as a result of artificial immunization or ap- 

 pearing in the blood of pneumonia patients at or near the time of 

 crisis, are easily demonstrated : the specific agglutination reaction 

 takes place between the intact pneumococcal cells, whether living 

 or dead, and the homologous antibody in the serum used. The re- 

 action varies from strict type-specificity to a broader species- 

 specificity, depending upon the nature of the antigen employed in 

 the production of the immune serum and that of the hapten par- 

 ticipating in the reaction. The somatic protein of the cocci and of 

 degraded or R forms of the organisms engenders agglutinins reac- 

 tive with all types of pneumococci, whereas the intact, virulent 

 forms of pneumococci or their unimpaired capsular constituents 

 evoke agglutinative substances strictly specific for the type of anti- 

 gen or component supplying the antigenic stimulus. In the latter 

 instance the reaction is one between the specific capsular polysac- 

 charide of the organism and its corresponding specific, immune- 

 serum globulin. Because of the simplicity of the technique required 



