DISCUSSION 



Converse: In a nine-year collaboration with Drs. Lawrence, Rapaport, 

 Thomas, Tillett and MulhoUand on this project, we have done 105 

 grafts on a group of normal human subjects, mostly medical students: 

 of these, 71 were first-set grafts, 18 repeat-set grafts and 16 "white 

 graft" reactions. In reviewing these 105 grafts we began to notice 

 certain differences concerning the individual specificity of the homo- 

 graft reaction in man that differed from that observed, for example, in 

 the reaction between two strains of inbred mice. There was consider- 

 able disparity in the duration of many of the first-set grafts. There was 

 also some disparity in the survival times of control grafts. To in- 

 vestigate this, two experiments were done, which I shall describe 

 briefly. 



In the first experiment two recipients (M. and H.) received two 

 successive grafts from N. The first graft was put on and then rejected, 

 and 15 days after the first a second graft was placed. The day after the 

 rejection of this second graft, which underwent accelerated rejection 

 (4-5 days), a third graft was placed, along with six control grafts from 

 different donors. There were five accelerated rejection reactions and 

 two 9- or 1 0-day survivals. The white graft reaction occurred because 

 of my impatience at the length of time that it took to perform four 

 successive grafts. We attempted to accelerate the interval between the 

 grafts and obtained this white graft reaction, which was interpreted by 

 our group as being an exacerbated state of hypersensitivity which 

 prevents the ingrowth of the vessels. 



A further experiment was set up as follows: a graft was placed on nine 

 recipients within the first 5-day interval after the rejection of the first 

 graft, and in all the nine cases there was a typical white graft reaction. 

 In control grafts placed at the same time as the white grafts five of them 

 had an accelerated rejection reaction. 



So I am just submitting for your consideration the possibility that in 

 man individual specificity is not as general as it is in the animal. Perhaps 

 this system offers a httle ghnt of hope in the possibiHty of some degree 

 of classification of tissue groups in the future. 



282 



