MECHANISM OF ANTIBODY FORMATION 95 



process analogous to the production of adaptive enzymes by bacteria. 

 The stress is laid on the assumption that contact with a sugar molecule 

 not normally fermented can impress on a bacterial enzyme a new 

 specific power of acting on this new substrate. 



A similar speculation related to the "adaptive enzyme" concept is 

 also advanced by Emerson (1945). He assumed that a disaccharide 

 such as maltose can make a transmittable print on a gene which then 

 conveys this to a protein in a manner complementary to that of the 

 gene yielding a specific enzyme. The gene then constructed on this 

 template should continue to produce the enzyme, even in the absence 

 of maltose. This is another version of the "adaptive enzyme" concept 

 which will be discussed below. 



b. Consideration of the Adaptive Enzyme Concept with Respect 

 to Antibody Production. The basic weakness in the theory proposed 

 by Burnet, et al. would seem to lie in the fact that it is patterned after a 

 concept which in itself is based on inadequate experimentation and 

 interpretation of the factors controlling the assumed production of, 

 or the increment in, the so-called "adaptive enzymes." As discussed 

 previously (Sevag, 1946), the analogy between the claimed mechanism 

 of adaptive enzyme formation and that of antibody production does 

 not appear to be valid. Burnet, et al. postulate that the antigen molecule 

 modifies a cellular proteinase which then is capable of synthesizing 

 an antibody molecule. That is, the proteinase adapts itself not to 

 metabolize the antigen but to synthesize antibody, a basic difference 

 from the assumed acquired ability of adaptive enzymes to metabolize 

 the specific substrate. Another noteworthy difference between anti- 

 body producing "adaptive proteinase" and "adaptive enzymes" is the 

 duration of the former for the liftetime of the host and the inheritabil- 

 ity of this character from parent to daughter host cells. In contrast, 

 the lifetime of an adaptive enzyme is postulated to be limited. That 

 is, it is formed when substrate is present and fails to function or form 

 when the substrate in question is removed. "Adaptive enzyme" and 

 "adaptive antibody" production concepts would have been more com- 

 parable if it could have been demonstrated that once the antibody 

 producing enzyme system is born in a host, it could adaptively function 

 to produce more antibody, provided the same antibody is introduced 

 from time to time into the system which has ceased to produce measur- 

 able antibody. The assumed permanency of the antibody synthesizing 



