HAMSTER CHEEK POUCH SKIN HOMOGRAFTS 97 



Table IV 

 Destruction of long-established pouch skin homografts by exposure of 



HOSTS TO homologous CELLS OR TISSUE ADMINISTERED BY VARIOUS ROUTES 



* The animals used for these tests were either L.S.H. hamsters bearing healthy C.B. 

 pouch skin grafts of at least 50 days standing, or M.H.A. hosts bearing C.B. grafts of 

 similar status and standing. In all cases the immunizing grafts were derived from the 

 original donor strain. 



t Leucocytes were obtained by resuspension of the buffy coat of blood. 



this manner the pouch skin graft soon became inflamed, there were 

 prominent intradermal haemorrhages followed by scabbing and 

 complete necrosis. Breakdown was usually complete within 

 two weeks. 



So far we have been unable to procure rejection of established 

 cheek pouch homografts by intradermal injection of their hosts 

 with suspensions of dissociated epithelial cells, prepared from 

 sheets of epidermis which had been separated enzymically from 

 homologous pouch skin (Billingham and Reynolds, 1952). This 

 failure can scarcely be ascribed to a lack of isoantigenicity on the 

 part of cheek pouch epithelium in the light of the various findings 

 presented. Present indications are that our epithelial cell suspen- 

 sions were non-viable at the time of inoculation. 



The "barrier" hypothesis 



All the evidence presented so far strongly suggests that the 

 anomalously long survival of pouch skin homografts stems from 



