206 IMMUNO-CATALYSIS 



toxin, toxoid and antitoxin. He was unable to offer any explanation for 

 this anomalous reaction. Stanley (1936) made similar observations 

 with tobacco mosaic virus and arrived at the conclusion that the 

 precipitin reaction which has been used as a measure of virus activity, 

 may not be used unreservedly as a measure of virus activity, for in the 

 case of inactive protein there is no correlation between the precipitin 

 titer and virus activity. His inactivated virus produced immune sera 

 which neutralized the viral activity. 



In the consideration of any of the systems belonging to the above 

 category, we must look into the presence or absence of a direct rela- 

 tionship between enzyme and antibody producing activities of the 

 proteins and their abilities to combine with respective antibodies with 

 or without the neutralization of their biological activities. While com- 

 bination of an antigen with its homologous antibody and other com- 

 binations with serologically non-specific inhibitors are stoichiometrical 

 reactions, the mechanism which governs the enzyme and antibody 

 producing activities of proteins are of catalytic nature. Stable stoichio- 

 metrical combinations with the specific active groups would be ex- 

 pected to block simultaneously all of the above named activities of 

 a given protein. It is, perhaps, for this reason also that in the form 

 of antigen-antibody complex an antigen may fail to produce a satis- 

 factory, if any, amount of antibody. In other words, when the specific 

 groups are completely blocked by specific antibody not only enzyme 

 activity, but also its ability to catalyze the production of specific anti- 

 body is inhibited. After reviewing the literature and on the basis of 

 his own experimental findings, Olitzki (1935) reported that when 

 the receptor groups of an antigen are saturated with antibody the 

 treated antigen is deprived of its capacity to develop specific antibodies. 

 He found that the injection of sensitized antigen together with free 

 antibody suppresses the formation of antibodies to 10 to 20 per cent 

 of the amount obtained with injections of antigens without serum 

 and the rate of reproduction is much slower. 



When larger amounts of antibodies are added, then the formation 

 of agglutinins can be completely stopped. As sensitized bacteria in vivo 

 and in vitro can be phagocytized, sensitized pneumococci and toxin- 

 antitoxin complexes can be attacked by proteolytic enzymes liberating 

 the cells or toxins without loss of activity, the failure of antigen in the 

 form of the antigen-antibody complex to stimulate the production of 



