PATHOLOGY OF THE IMMUNE RESPONSE 



The necessary postulates can best be discussed in relation 

 to Figure 8, p. 65, which was designed to show the response to 

 antigen of specifically conditioned cells at different levels of 

 maturity. If we consider a mature lymphocyte which by 

 contact with the relevant antigenic determinant has been 

 directed along the path of activation, settlement in an appro- 

 priate tissue niche and proliferation, we have to picture a 

 process of what might be called rejuvenation to the 'primi- 

 tive stem cell' phase followed by active proliferation with 

 gradually increasing maturity of the descendant cells. It is 

 reasonable therefore to suggest that the cell's reactivity to 

 subsequent contact with the specific antigenic determinant 

 changes progressively to a more and more immature type, 

 that is, that at a certain stage, probably just before prolifera- 

 tion is well established, the cell can be destroyed by a second 

 contact with the determinant. It might well be that there is 

 some analogy between the radio-sensitive phase of antibody 

 production and this postulated phase of specific susceptibility 

 to new contact with antigenic determinant. Such a view 

 would have a number of implications in line with the 

 experimental findings. 



Consider first a mutant cell, say a lymphocyte, which is 

 specifically reactive with an amino-acid grouping present 

 on the body's own plasma protein. With first contact the cell 

 is activated and becomes progressively more sensitive to the 

 antigenic determinant. This is ubiquitous inside the body 

 and before the stage of proliferation is reached the inevitable 

 secondary contacts will ensure that the cell is destroyed 

 or rendered dormant. No proliferation and no antibody 

 results. 



Next consider a foreign antigenic determinant stimulating 

 a cell of appropriate character. This settles down, let us 

 assume, in the local lymph node. Here there is a very effective 

 mechanism for the phagocytosis of foreign particles by littoral 

 cells and unless the antigen concentration is very high most 

 stimulated cells will cross over the vulnerable stage without 



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