92 IMMUNO-CATALYSIS 



reticuloendothelial cells of liver and spleen for years as 

 evidence for the persistence of the same individual cells, 

 Burnet concluded : "we can see no escape from the conclusion 

 that the antibody-producing mechanism can be transmitted 

 to descendant cells by some hereditary process. 

 (7) "The tjfe of antibody 'produced varies (a) according to the 

 species used, (h) with the age of the animal, and (c) according 

 to the nature and frequency of the antigenic stimuli. The 

 change in character of the antibody following repeated re- 

 inoculation is the difference of most theoretical importance. It 

 would indicate that an antibody-producing mechanism once 

 established can be further modified by new antigenic con- 

 tact. 



Of the criteria offered by Burnet, et al. in support of their theory, 

 criteria one to four can be explained by the observations considered in 

 the preceding discussions in relation to the factors controlling the im- 

 mune response to an antigen, and those related to the antigen-antibody 

 balance during the process of immunization. The most challenging of 

 these criteria are those condensed in paragraphs five and six. It is here 

 assumed that antibody production continues long after the antigen has 

 disappeared from the body. It is, therefore, concluded that antibody 

 production is a characteristic which is acquired not only by the cell 

 proteinases but also transmitted to the descendant cell proteinases. In 

 other words, it is an acquired characteristic inheritable by generations 

 of cells during the lifetime of the host. In support of these assertions 

 these authors cite, in particular, the lifetime persistence of immunity 

 against measles and yellow fever virus. In the case of yellow fever, 

 based on an observation by Sawyer, they stated that "there is direct 

 evidence that a single infection may induce the formation of antibody 

 which can be detected in the serum 75 years later." 



Landsteiner (1945), in reference to the nature of long-lasting 

 immunity, and certain claims that antigens leave impressions upon the 

 antibody-producing cells which last after the disappearance of the 

 antigen, made the following statement: "The fact that immunity can 

 last for many years would be a decisive proof, but in the most striking 

 case of virus infections (smallpox, measles, yellow fever), the perma- 

 nence of active virus cannot be excluded." According to Rous (1946), 



