1 24 IMMUNO-CATALYSIS 



every primary amino group in the original antibody molecule. Acet- 

 ylated antibody lost to a great extent its capacity to precipitate the type 

 specific polysaccharide. When relatively high concentrations of type 

 specific carbohydrate were added to the acetylated antibody, a precipi- 

 tate was formed. The original antibody gave H — | — \- precipitate with 

 1:1,024,000 carbohydrate dilution; in contrast, acetylated antibody 

 gave H — I — h with 1:4000 and + precipitate with 1:8000 carbohy- 

 drate dilution. These results were interpreted to indicate, besides the 

 amino groups, the presence of certain other reactive groups likewise 

 involved in the precipitation reaction. 



Since formalized antibody protein gave no precipitation test the 

 amino groups in the native antibody were believed to be concerned in 

 the union of the antibody with the carbohydrate. Deformalization of 

 the antibody restored its serological specificity. The loss of serological 

 specificity of the formalized antibody was considered presumably due 

 to the conversion of the -NHg to -N^CHs group. Conversely the 

 esterification of the — COOH group of the antigen carbohydrate de- 

 prived it of its reactivity with the native antibody. Saponification of 

 the esterified carbohydrate fully restored its reactivity. Though the 

 saponified carbohydrate still contained methyl groups (as a result of 

 the treatment of the carbohydrate with diazo-methane in the esteri- 

 fication experiment) bound both on the primary -NH2 group of the 

 parent carbohydrate and as a methoxyl group attached probably to 

 one of the hydroxyl groups, unlike the inert ester, it reacted readily 

 with antisera. These results showed that a free -COOH group in the 

 carbohydrate was of primary importance in rendering it serologically 

 reactive. In other words, the union of the free -COOH group in 

 carbohydrate with a free — NH2 group in the antibody was considered 

 possibly necessary for the serological reactions. The normal globulin 

 molecule does not possess this serologically reactive "free amino group." 



The presence of a serologically reactive "free amino" group in anti- 

 body globulin and not in normal globulin was also shown by Goebel 

 and Hotchkiss (1937) with substances containing organic acid radi- 

 cals. They found that artificial azoprotein antigens containing organic 

 acid radicals, quite unrelated in chemical constitution to glucuronide 

 or galacturonide, precipitated in antipneumococcal horse sera. Antigens 

 prepared from j^-aminobenzene carboxylic and sulfonic acids, though 

 not reactive in normal horse serum, precipitated in antipneumococcus 



