HAMSTER CHEEK POUCH SKIN HOMOGRAFTS 9I 



of the cheek pouch have been compared with those of similar 

 grafts transplanted orthotopically to recipient areas prepared in 

 the skin of the trunk (Billingham, Ferrigan and Silvers, i960; 

 Cohen, 1961). Furthermore, it has been shown that the privilege 

 extended to foreign grafts in the pouch is not absolute: homo- 

 grafts undergo prompt destruction if implanted into the pouches 

 of previously sensitized hosts, and the lives of long-established 

 homografts in the pouches of normal animals are soon terminated 

 if their hosts are sensitized by means of orthotopic skin homo- 

 grafts from the original donor strain. 



In the course of studies designed to elucidate the basis of the 

 privileged status of the cheek pouch, the fate of homografts of 

 cheek pouch "skin", transplanted to the environment of normal 

 skin, has been investigated. A preliminary account of this work 

 and some implications of the findings constitute the subject 

 matter of this paper. 



Materials and methods 



Adult hamsters belonging to three different, partially inbred 

 strains of remote common origin, M.H.A., C.B. and L.S.H., 

 were employed. Although none of these strains as yet can properly 

 be designated as isogenic, each is completely uniform with respect 

 to its histocompatibility genes — i.e., it is isohistogenic (Billingham 

 and Silvers, 1959). The three donor/ recipient strain combinations 

 employed and the median survival times of medium-sized 

 orthotopic homografts of normal trunk skin transplanted between 

 them are set out in Table I. It may be added that hamster stocks 

 in general are anomalous in that the number of demonstrable 

 segregating histocompatibility genes is very small. Analyses by 

 Billingham, Sawchuck and Silvers (i960) have shown that the 

 present strains differ only with respect to one or two important 

 histocompatibility loci. Nevertheless, the homograft reactions 

 promoted by these differences are just as powerful as, and 



