THE FACTS OF IMMUNITY 



by Taliaferro (1949). He holds that we should consider not 

 any particular type of cell but what he calls the mesenchymal 

 reserves which comprise reticular cells, macrophages and 

 the lymphoid series. He believes that lymphocytes can 

 develop into macrophages or plasma cells. 



My own working picture of the situation is frankly based 

 on a desire to obtain the simplest interpretation of the cellular 

 basis of antibody production which is not clearly at variance 

 with the available facts. This is that cells of any clone of 

 mesenchymal cells may, under appropriate conditions of the 

 internal environment, take the form of stem cell, macro- 

 phage, lymphocyte or plasma cell and that the observed form 

 is essentially a reflection of the function it is performing at 

 the time of fixation. In all probability the fibroblast should 

 be included as a product of these mesenchymal cells, but the 

 possibility of its back-conversion to one of the specifically 

 functioning types is not established. 



7. Summary 



This outline of the facts of immunity is selective and incom- 

 plete. Its purpose is simply to present the aspects which seem 

 to be specially significant for any biological interpretation 

 of immunity. From our own particular point of view the 

 crucial points are probably : 



(i) In some way there is a recognition of self components 

 from 'not self; from the facts of immunological tolerance 

 the recognition mechanism is laid down toward the end of 

 embryonic life. Any such mechanism must differentiate 

 between self and not self in one or both of two ways : 



Either [a) All significant antigenic patterns of the body 

 are positively recognized by the antibody-producing me- 

 chanism. Foreign patterns, because they are not recognized, 

 provoke an immune response ; 



Or {b) All the possible types of foreign and antigenic 

 determinant can be positively recognized as foreign and 

 hence calling for an immune response. 



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