ANTIGENS AS BIOCATALYSTS 43 



twice-crystallized pepsin, nor with the serum proteins from the homol- 

 ogous species. 



These findings demonstrate beyond doubt that pepsin protein is 

 specifically antigenic. It also appears that pepsin retains the serologi- 

 cal specificity of pepsinogen to an appreciable degree. On the other 

 hand, pepsinogen is serologically an independent entity. Its activation 

 into pepsin, associated with chemical changes (Herriott) partially 

 retains this specificity. 



Antibody against Catalase. After the isolation of beef liver catalase 

 by Sumner and Dounce (1937) and horse liver catalase by Bounce 

 and Frampton (1939) in crystalline form, Tria (1939), and Campbell 

 and Fourt (1939) reported the immunization of rabbits with crystalline 

 beef catalase. Tria immunized rabbits by injecting them with 12.5 

 mg. of enzyme every three days for three weeks in the first set of ex- 

 periments. In a second set of experiments he started with 1.25 mg. of 

 enzyme and gave gradually increasing doses. The immune sera had 

 high anti-catalase activity. The sera reacted in 1:10 optimal dilution 

 with a solution of catalase containing 0.1 to 1 mg. Determining the 

 anti-catalase activity of the serum quantitatively he obtained 4 anti- 

 catalase units in 1 ml. serum. A 50-fold purified anti-catalase isolated 

 from the catalase-anti-catalase precipitate after dialysis had 2200 

 anti-catalase units per g. of antibody. 



Anaphylactic experiments by Tria also showed the presence of anti- 

 body in the serum of guinea pigs actively immunized against beef 

 and horse liver catalase. Anaphylactic shock resulted in the death of 

 the immune animals within a few minutes. 



The results of anaphylactic experiments aiming at a serological 

 differentiation of the species specificity of beef, lamb, and horse liver 

 catalases were inconclusive. The precipitation tests by Campbell and 

 Fourt likewise demonstrated the formation of antibody against beef 

 liver catalase. The results obtained from experiments involving the use 

 of dog and horse liver catalases as antigens likewise did not yield con- 

 clusive information regarding the question of the species specificity of 

 catalases. 



Summary and Conclusions. The formation of antibodies in the 

 animal system in response to antigenic stimuli has been discussed from 

 various viewpoints. The stoichiometrical relationship underlies all 

 known chemical changes— simple combination, decomposition, double 



