246 IMMUNOLOGY 



Some strains of C. diphtheriae produce toxin of such potency 

 that 0.001 c.c. will kill a 250 gram guinea pig within four or five 

 days, while other strains produce toxins of exceedingly low 

 potency; i.e., the corresponding minimum lethal dose is 0.10 c.c. 

 or more. Maver (1930), working in Jordan's laboratory, carried 

 out an extensive investigation of toxin production of C. diphtheriae 

 in synthetic media.* She reports that "the simple mono-amino- 

 acids, such as alanine, phenylalanine, valine and especially glycine, 

 were more effective in stimulating growth in a synthetic medium 

 than the more complex mono-amino-acids that were tried." She 

 found that a modification of Braun and Hofmeier's synthetic 

 medium containing glycine, a fourfold amount of cystine and 

 asparagin or ammonium succinate instead of sodium asparate was 

 quite satisfactory. One strain of C. diphtheriae grown in this 

 medium yielded a toxin of which 0.1 c.c. constituted a minimum 

 lethal dose and 0.0001 c.c. a skin test dose. 



When broth containing toxin is subjected to dialysis, the toxin 

 dialyzes slowly but relatively more rapidly, according to Wells, 

 than proteins are observed to dialyze. The toxin is precipitated 

 by protein precipitants such as alcohol, ammonium sulphate, etc., 

 which indicates that it is either a protein or closely associated 

 with the proteins. In this connection it is interesting to note that 

 proteolytic enzymes are said to destroy them. Toxins may be 

 preserved for long periods of time if kept at a low temperature 

 and protected from light. Both ultraviolet light and roentgen rays 

 destroy them. 



Effect of Heat, Drouth, and Chemicals on Toxins. — When a 

 solution of diphtheria toxin is boiled for five minutes both its 

 toxic and antigenic properties are destroyed. The toxin is slowly 

 reduced in potency when heated to 45° C. and more rapidly de- 

 stroyed when exposed to temperatures of 60°, 70° and 80° C, 

 respectively. Dried toxin withstands 100° C. but is destroyed at 

 150° C. Roux and Yersin (1889) found that small amounts of 

 acid remove the toxic property and that the latter is restored 

 when the acid is neutralized providing the neutralization is ef- 

 fected within a certain ascertained period of time. Wellsf (1929) 



*Muller, J. H., and Miller, Pauline A., describe a new gelatine-hydrolysate 

 medium that favors the production of diphtheria toxin of high potency, J. 

 Immunol. 40: 21, 1941. 



tWells, H. G. : Chemical Aspects of Immunity, Reinhold Publishing Corpora- 

 tion. 



