THE UNIQUENESS OF THE INDIVIDUAL 



provided only that it could rid itself of the tumour as soon as 

 it became immunologically mature. Unfortunately, the effect 

 of exposing the foetus to the malignant cells would be to 

 prevent that very process of maturation, so that death early 

 in post-natal life would be almost inevitable. 



When therefore we think of the immunological relationship 

 between the mother and the foetus, we must read the relation- 

 ship both ways round: the foetus must not be allowed to 

 immunize the mother, and the mother must not be allowed to 

 weaken the immunological defences of the child. It is for this 

 reason, and for no other one sufficient reason, that the blood 

 systems of the mother and the foetus must be strictly separate 

 all the time, in every place, and at every level down to the finest 

 capillary vessel. 



Beyond this, the concept of immunological tolerance has 

 implications which are deeply philosophical, in the worst sense 

 of the word, for it bears directly upon the problem of the 

 recognition and awareness of The Self. Why do not the cells 

 which undertake immunological responses react against con- 

 stituents of the body in which they themselves are housed? 

 W^hy are not ''auto-antibodies'' regularly formed? Alas for 

 Naturphilosophie^ the problem is soluble and can be clearly put. 

 The question of manufacturing auto-antibodies (or otherwise 

 reacting) against antigens of the type that cause transplanta- 

 tion immunity cannot arise in practice, because, as I have 

 already explained, these antigens are uniformly represented in 

 all the tissues of a single individual, not excepting his antibody- 

 forming cells. Being part of the fabric of his o^vti antibody- 

 forming cells, an individuaPs own ""transplantation antigens'* 

 cannot be reacted upon as if they were foreign. But that does 

 not explain why, for example, muscle protein, or any proteins 

 distinctive of skin or nerve, should not appear foreign to 

 an individuaPs own antibody-forming cells. The answer, we 

 believe, is that his antibody-forming cells develop in the con- 



183 



