Comparison of the Combining, Antigenic, and Toxic Properties of Chemically Altered Diphtheria Toxoid and Toxin

Summary Azodyes were prepared from crude and from purified diphtheria toxoid by coupling them with the diazonium salt of arsanilic acid. The dyes obtained were purified by dialysis and precipitation with acid at about pH 4 and pH 3. The dyes had practically lost their immunizing power but retained their combining power as measured by the Ramon test. The specific toxic and the non-specific reaction-causing properties of the dye were approximately the same as those of the original toxoid or toxin. Micro arsenic and nitrogen determinations were made on the toxoid dye. High values were obtained for the ratio of arsenic to nitrogen, hence a high content of cyclic amino acids in the toxoid or else a decomposition during the dye formation is assumed.