DISCUSSION 283 



Silvers: In the work that you have just mentioned, there is very good 

 evidence that at least some antigens are shared by some medical 

 students. However, in the case of the work presented by Dr. Lawrence, 

 I don't think his results ever indicated the existence of shared antigens. 

 What is your explanation for this ? 



Converse: It must be remembered that the effects of cell transfer on 

 the "test" grafts were judged as significant only in terms of their 

 relation to the behaviour of control grafts on the same recipient. For 

 this reason, it would appear that the bearing of such variables as genetic 

 disparity upon the observations reported by Dr. Lawrence was greatly 

 diminished. The focus in the cell transfer study was on individuals. 

 Evidence of cross-reactions begins to appear when an entire group of 

 subjects is studied, and this was not the end point of Dr. Lawrence's 

 experiments. 



Lawrence: It should be clearly understood that accelerated rejection of 

 unrelated "control" first-set skin grafts requires prior hypersensitization 

 of the graft recipient with the test graft so that it elicits a white graft 

 reaction. This manoeuvre will elevate the intensity of the homograft 

 reaction, not only to the test graft itself^ but carry over to the control 

 grafts. Rapaport, Converse, Thomas and I have also found that if 

 leucocytes (or their extracts) are used instead of an orthotopic skin 

 homograft to sensitize, they appear to function as even more potent 

 antigens. The latter mode of sensitization will bring out the pheno- 

 menon of sharing of transplantation antigens even more regularly and 

 to a greater degree, that is to include more individuals. There is quite 

 a difference between this sort of dehberate hypersensitization procedure 

 and merely placing one test and one control graft on an individual who 

 has had a cell transfer. 



Brent: Dr. Lawrence, if your material is neither an antibody nor an 

 antigen, what is it ? 



Lawrence: We do not know the biochemical nature of transfer factor. 

 It is, however, a material that transmits immunological information to 

 human recipients. 



Brent: I would like to add that with Dr. Lawrence we at University 

 College have tried very hard to get this transfer factor to work in the 

 guinea pig and that this attempt has completely failed. Dr. Lawrence, I 

 believe that you have more recently been able to transfer reactivity in 



