ANTIBODIES TO PNEUMOCOCCUS 407 



Protective Antibodies 



To resolve the protective action of antipneumococcic serum into 

 the causal elements participating in the phenomenon is a difficult 

 task. There is the innate defense mechanism of certain animal spe- 

 cies ; the functional ability of various animals to respond to anti- 

 genic stimuli, as manifested by the elaboration of antibodies of dif- 

 ferent properties ; the interaction of tropins or opsonins, cocci, 

 and white blood corpuscles ; and the natural or the artificially en- 

 hanced avidity of fixed tissue cells for pneumococci. As in other 

 aspects of antipneumococcal immunity, the communications of the 

 Klemperers (1891) 724 " 5 were prophetic in suggesting that the se- 

 rum of animals after being injected with derivatives of Pneumo- 

 coccus developed the ability to render the cocci susceptible to the 

 action of blood cells and body cells and, therefore, harmless to the 

 injected animal. The authors erroneously ascribed the protective 

 action of the serum to an antitoxic effect, but the assumption does 

 not invalidate the observation. Eyre and Washbourn (1898), 374 by 

 injecting mice with mixtures of varying amounts of antipneumo- 

 coccic horse serum and virulent cultures of pneumococci, were the 

 first workers to demonstrate quantitatively the protective power 

 of specific immune serum. The authors later applied the method to 

 the standardization of therapeutic serum and, in doing so, discov- 

 ered that the method could be employed to distinguish between dif- 

 ferent varieties of the organism.* 



Neufeld and Haendel (1910), 991 using the protection test for 

 evaluating the strength of immune serum, confirmed the observa- 

 tions of Eyre and Washbourn on the existence of types of pneu- 

 mococci with different serological affinities and thus established the 

 protection test as a means for the classification of pneumococci 

 into different serological types. Neufeld and Haendel at first em- 

 ployed 0.2 cubic centimeter of immune serum, which they in- 



* Wassermann (1899)i*9i sought to locate the origin of protective substances, 

 and from his experiments concluded that the antibodies apparently were 

 formed in the bone marrow, and that the lymph nodes, thymus, and spleen 

 merely served as reservoirs. 



