344 IMMUNOLOGY 



Formalized Rabbit Serum as an Antigen. — Lanclsteiner and 

 Lampl (1917) also showed that formalized rabbit serum used as 

 antigen would stimulate antibodies when injected into rabbits 

 that reacted only with formalized rabbit serum and not with form- 

 aldehyde-treated proteins of other species. This would indicate, 

 as Wells (1929) has pointed out, that "the occupation of an amido 

 group, e.g., lysine or alanine, by the methylene radical is almost 

 devoid of any effect on specificity, and that a marked chemical 

 change can take place in a protein without noticeable effect on the 

 structural or species specificity." When formaldehyde is added 

 to a protein, it couples with the nitrogen of the amino (-NHo) 

 group with the splitting off of water, as may be seen in the follow- 

 ing reaction of alanine and formaldehyde : 



H H 



H— C— H H H— C— H 



H— C— N i H, + O i = C = H— C— N=CH,, + H.,0 



I '- ' I 1 " ' 



C=0 H C=0 



OH OH 



This condensation removes the basic properties of the amino acid 

 and permits the acid groups to become dominant. This is the 

 basis of Sorenson's "formol" titration method for amino acids. 

 Recent Work on Iodized Antigens. — Wormall (1930) and 

 Jacobs (1932) have recently carried out extensive studies on 

 iodinated sera. The latter prepared antigens, i.e., iodized serum 

 proteins, in dilute ammonium hydroxide solution and also without 

 acid or alkali and compared them immunologically. Jacobs also 

 investigated the loss of original specificity as a result of iodine 

 entering the protein as well as the specificity of the antibodies for 

 iodized antigens and ascertained the amount of iodine necessary to 

 alter the antigen. He also confirmed the observations of Wormall 

 (1930) that diiodotyrosine suppressed the formation of specific 

 precipitates that would ordinarily result when iodinated protein 

 and its antiserum are mixed. This is another example of sup- 

 pression phenomena frequently described by Landsteiner. Jacobs* 

 summarizes the results of his work as follows : 



♦Jacobs, J.: J. Immunol. 33: 3G1, 1932. 



