MECHANISM OF ANTIBODY FORMATION 135 



Stated that since antitoxin, when precipitated by a precipitin, can still 

 combine with toxin, different groups must be involved in the two re- 

 actions. Eagle (1936) stated, as previous investigators had shown, that 

 a molecule of antibody can function either as an antibody or as an 

 antigen. In the former capacity, it combines with homologous anti- 

 gen; in the latter capacity the antibody molecule is itself precipitated 

 by an antibody to serum protein. Experimental details of Eagle's 

 studies differ from those of Eisler, Smith and Marrack in that the 

 latter did not saturate antitoxin vdth toxin or precipitin prior to the 

 addition of precipitin or toxin. In Eagle's experiments horse antitoxin 

 precipitated by a large excess of a rabbit antiserum against horse serum 

 and presumably saturated with precipitin, nevertheless retained almost 

 its original neutralizing activity. Antitoxin so completely saturated with 

 toxin as to form a highly toxic compound combined with a rabbit pre- 

 cipitin against horse serum. From these and numerous other serological 

 data, it is to be seen that antibody globulin molecules possess specific 

 reactive groups not present in the normal globulin molecules. 



e. Further Experimental Data Concerning the Presence of a Com- 

 mon Group in DiflFerent Antibodies from a Species of Animal. Ando 

 and his associates (1937, 1938) immunized rabbits, ponies and horses 

 with diphtheria toxin-antitoxin flocculi, and with the specific precipitates 

 of pneumococcal type specific carbohydrate and its antibody in its 

 purest form. The serological tests were carried out by the optimal- 

 proportions-method of Dean and Webb and the absorption technique. 

 They found that the precipitin-versus-antitoxin absorbed diphtheria 

 antitoxin in the range of optimal proportions and also at higher ratios. 

 Pneumococcal antibody, however, was absorbed by precipitin-versus- 

 antitoxins only within the range of the mixtures containing far less 

 amounts of anti-pneumococcal serum than that in the optimal propor- 

 tion. Precipitin-versus-antibacterial antibody absorbed anti-pneumococ- 

 cal antibody, but diphtheria antitoxin was absorbed by the same 

 precipitin only in the secondary zone and not in the primary or main 

 zone. These results were interpreted by the authors to signify that 

 various antisera contain larger amounts of antibody against the homol- 

 ogous than the heterologous immunizing flocculi. In these studies as 

 indicated above the horse antisera against different flocculi reacted vdth 

 homologous as well as heterologous antisera. 



Treffers and Heidelberger (1941) examined the properties of spe- 



