ANTI-ENZYME IMMUNITY 257 



fluid. The optimum activity was at pH 7, Normal horse serum in 

 amounts of 0.4 to 2 ml. (1 to 10 dilution) had no effect on the enzyme 

 activity. 



The absence of inhibition of the proteolytic activity of the toxin by 

 normal horse serum and the inhibition of its activity by antitoxin was 

 determined (Table XII). 



The volume of the reaction systems was made to 10 ml. (0.40 g. of 

 gelatin); pH=7 (without buffer); t=40°; period 24 hours; toluol and 

 cysteine were added under an atmosphere of nitrogen. The test solu- 

 tion for titration was 2 ml. 



The above data show that the proteolytic activity of the toxin prep- 

 aration of CI. welchii was inhibited 52 per cent. 



2. Antibody Against Bacterial Proteinases 



Von Dungem (1898) reported that the sera of persons infected with 

 anthrax bacillus, cholera vibrio and staphylococcus contain antipro- 

 teolytic antibody. These antisera inhibited the hydrolysis of gelatin 

 by the proteolytic enzymes of these microorganisms. The enzyme 

 preparations used in these tests were either broth culture filtrates or 

 bacterial extracts which had been precipitated with alcohol. In con- 

 trol tests, gelatin was hydrolyzed by these preparations. In contrast, 

 in the presence of 0.5 to 0.002 ml. of specific immune sera, the hydroly- 

 sis of gelatin by the enzyme preparations was completely or partially 

 inhibited. Also, the sera of animals immunized with the enzyme prepa- 

 rations strongly inhibited their activity. Normal serum exercised no 

 inhibition. The sera of two patients suffering seriously from osteo- 

 myelitis inhibited twenty times as much staphylococcal proteolytic 

 enzyme as was inhibited by normal human serum. The inhibitory 

 action of the antisera was specific. 



Dochez and Avery (1916) reported that antipneumococcal serum 

 exercised marked inhibitory action on the growth of homologous 

 pneumococcus during a three hour growth period as compared with 

 the absence of inhibitory effect with normal horse serum. The inhibi- 

 tion by homologous immune serum was greater than by heterologous 

 (species) immune serum. These facts showed that, as they concluded, 

 some property of immune serum adversely affected the circumstances 

 of multiplication. 



