CELLULAR REACTIVITY REQ^UIRED 



is being assumed is that each immunologically conditioned 

 cell carries at some accessible sites reactive groupings 

 equivalent to those by which an antibody globulin molecule 

 attaches to the specifically corresponding antigenic deter- 

 minant. When a reactive site makes specific adsorptive contact 

 with an antigenic determinant, this union is assumed to act as a 

 trigger initiating intracellular processes whose character and 

 result will depend on the various factors already mentioned. 



Proliferation 



Destruction 



Antigen concentration — ► 



Fig. 8. The changing reactivity postulated for immunologically 

 conditioned cells at various stages of maturity. (See text.) 



Figure 8 has been devised to indicate the types of reactivity 

 which need to be postulated to cover the various phenomena 

 of immunological tolerance and of antibody production. 

 The ordinates correspond to the main types of reactivity that 

 are significant from the point of view of cell numbers. The 

 zero point corresponds to no reaction, above this proliferation, 

 and — where the lines are thickened — the development of 

 plasma cells and antibody production, are indicated. Below 

 the zero point we have inhibition of proliferation extending 

 down to complete dormancy or destruction. The abscissae 

 represent effective concentration of antigenic determinants. 

 This will almost certainly be a complex function in which 



5 65 



BC 



