ANTI-ENZYME IMMUNITY 193 



Schubert (1933), in a study on the retardation of invertase activity by 

 homologous immune sera, found that from pH 3 to pH 4.2, normal 

 and immune sera produce the same effect, the inhibiting property of 

 immune serum vanishing. The presence of either normal or immune se- 

 rum in this acid region enables the invertase to retain 90 to 92 per cent 

 of its activity at pH 4.5 to pH 5. From pH 5 on, on the alkaline side, 

 invertase activity is not altered in the presence of normal serum. In 

 contrast, the retardation by immune serum between the range of pH 

 4.5 to pH 6.5, respectively, rose from to 25.6 per cent. (At pH 6.5 

 the activity of invertase per se was 50 per cent of its activity at its opti- 

 mum pH of 4.5.) These findings showed that in the acid region the 

 combination between the invertase and anti-invertase was completely 

 prevented, and that within a range of pH 5 to 6.5 union took place 

 producing retardation of the invertase activity. 



In view of these facts, a review of the literature regarding the effect 

 of pH on antigen-antibody combination is necessary. Mason (1922) 

 stated that precipitation reactions occurred between pH 4.5 and 9.5 

 and outside this range, immune precipitates dissolved. Schmidt (1930) 

 found that diphtheria toxin and antitoxin flocculated rapidly at pH 

 5.0 to pH 8; outside of this range the toxin is partly destroyed and 

 the flocculation is slow or does not take place. 



Bayne-Jones (1924), studying the effect of pH 4.5, 6, 8 and 9 on 

 the rate of toxin-antitoxin flocculation, stated that the results of titra- 

 tions at pH values beyond the range of 6.4 to 8.4 were irregular and not 

 significant. When the toxic broth was made more acid or alkaline than 

 pH 6.4 to 8.4 non-specific precipitates were produced in the broth, 

 which obscured any flocculation due to the union of toxin and anti- 

 toxin. 



Brown (1934), in a study of the effect of pH, ranging from 8.0 to 

 4.77, on the optimal flocculation values, stated that the greater the pH, 

 the more pneumococcal Type I and Type II polysaccharide is necessary 

 to combine with the antibody. Appreciable effect both on the amount 

 and speed of flocculation was noted below pH 6.26. The pH effects 

 were very similar to those of increasing salt concentration; that is, the 

 more salt in the flocculation mixture, the more antibody was necessary 

 to form a stable compound with the polysaccharide. 



Marrack and Smith (1930, 1931) stated that they observed no effect 

 at pH values from 8.0 to 6.6 on the ratio of antibody to antigen in the 



