THE SYNTHESIS OF PROTEINS 37 



hypothesis for the formation of antibodies must account for the follow- 

 ing facts (Burnet, Freeman, Jackson, and Lush, 1941 ; Landsteiner, 



1945): 



1. They are proteins which react specifically with their antigens. 



2. They may be produced by so many different antigens that it is 

 extremely unlikely that even one molecule of all possible antibodies ex- 

 ists in the normal animal. 



3. They are produced in great quantity as compared to the quantity 

 of antigen which causes their formation. 



4. Antibody continues to be formed after the antigen has disappeared. 

 This statement unfortunately cannot be considered an experimental fact 

 since the evidence, although strong, is not conclusive (cf. Burnet, Free- 

 man, Jackson, and Lush, 1941 ; Landsteiner, 1945). There is no doubt 

 that antibody continues to be formed long after any antigen can be 

 detected experimentally in the circulation, but it is possible to assume 

 that minute quantities of antigen are still present in the cells. As Burnet 

 points out, this question is of fundamental importance to the theories 

 of antibody formation proposed by Ostromuislenskii (1916), Koltzofif 

 (1928), Mudd (1932), Pauling (1940), Pauling and Campbell (1942), 

 and Sevag (1945 ) , since these hypotheses all include the assumption that 

 antibody is formed as a result of some type of reaction between antigen 

 and globulin. Harris and Ehrich state that the decomposition products 

 of antigens occur autocatalytically. 



5. The chemical nature of antibodies may be different in different 

 species or in animals of different ages. 



This statement is open to question since no antibodies have been iso- 

 lated in pure form. 



6. Antibodies are formed only in the animal receiving the antigen. 

 Injection of another animal with antisera (passive immunization) re- 

 sults in rapid disappearance of antibody and not in the formation of 

 more antibody. This fact precludes any purely autocatalytic mechanism 

 for the formation of antibodies, unless secondary hypotheses are added. 



7. Antibodies are formed in cells, probably in the lymphocytes 

 (Dougherty, Chase, and White, 1944, 1945; Dougherty and White, 

 1945; Harris and Ehrich, 1946). 



animals and have been found in all serum fractions (cf. Landsteiner, 1945, p. 133). 

 These results also indicate that the antibody itself may be a distinct protein ratlior than 

 a modified globulin. On the other hand, young animals which do not form antibodies 

 readily are said to possess very small amounts of serum globulin (Orcutt and Howe, 

 1922). 



