OPENING REMARKS 



H-2) and "weak" (non H-2) antigenic differences, accompanied 

 by evidence that these weaker barriers of incompatibiUty are so 

 much easier to break down than those erected by loci equivalent 

 in strength to H-2. Nor should we forget the discovery of certain 

 isolated phenomena which, though at present unexplained, may 

 be looked back upon as being of crucial importance : the strange 

 outcome of the intravenous injection of dissociated epidermal cells 

 into rabbits; the privileged position of the hamster's cheek pouch; 

 the anomalous behaviour, in guinea pigs, of thyroid homografts 

 which have been allowed to reside for some months in the anterior 

 chamber of the eye; the influence of an ovarian homograft on a 

 later homograft of skin; and so on. 



This is an inspiriting record, and one which workers in the field 

 of transplantation research can take pride in. But — let us not 

 forget that we are still quite ignorant of the proximate cause of the 

 death of any homograft; the role of serum antibodies in transplan- 

 tation immunity is still very far from certain; the chemical analysis 

 of transplantation antigens is httle more than embryonic ; we are 

 ignorant of much of the dynamics or kinetics of transplantation 

 immunity, particularly as it concerns the origin and duration of 

 sensitivity under different conditions; the relationship between 

 tolerance and paralysis has yet to be laid bare; and, above all, we 

 know of no harmless and lastingly effective way to subdue the 

 homograft reaction in adult animals. We still have a very long 

 way to go. In short, I think self-satisfaction and self-reproach 

 should be about evenly balanced in our minds ; and in that spirit 

 let us begin this conference. 



