THE UNIQUENESS OF THE INDIVIDUAL 



mouse contain no "transplantation antigens'* not also present 

 in its kidney cells or leucocytes or spleen. The hall-mark that 

 distinguishes a particular individual is to be recognized in all 

 his living cells and must therefore be stamped upon some 

 constituent which all cells share in common. What, then, is the 

 chemical nature of the substances which leave a homograft, 

 enter the lymphatics, reach the regional lymph nodes and there 

 set in train the reaction that ultimately causes the homograft 

 to be destroyed? 



On the face of it, such a problem should not be too difficult 

 to solve; yet it is not unjust to say that fifty years of research 

 upon the problem of incompatibility had not, until very 

 recently, provided us with even the beginnings of an answer. 

 For the antigenic substances are grievously unstable. If a 

 living tissue is heated for a few minutes to a temperature of 

 49° C. (which is not so much hotter than a hot bath), or thrice 

 alternately frozen solid and then thawed, or frozen solid and 

 then dried under a high vacuum in the frozen state, it loses its 

 power to provoke immunity. All these treatments kill cells, 

 but they do so in the humanest possible way, i.e. in the way 

 that does the least possible unnecessary damage to their fine 

 structure — and cells must surely be killed if they are to be 

 separated into their several chemical or anatomical fractions. 

 So we had to resign ourselves to a belief belonging conceptually 

 to the dark ages, viz. that the power to cause transplantation 

 immunity was a prerogative of living cells. 



The findings w^hich I am now about to describe^ began with 

 the discovery that it is possible to kill and disintegrate cells 

 without destroying the substances that cause transplantation 

 immunity. It is done by exposing cells to very loud and very 

 high-pitched sound; in effect, then, to vibrations of high 

 ampUtude and frequency. The amplitude of the vibrations 



1 R. E. Billingham, L. Brent and P. B. Medawar, Nature, 178, p. 514, 

 1956. 



L 161 



