DISCUSSION 115 



might influence the survival time of ordinary skin grafts transplanted 

 to the chest of the hamster. 



Billingham: A colleague, thinking along lines such as those you have 

 outlined, has suggested that the connective tissue might selectively 

 absorb and inactivate the antigens. What appears to be a weakness of 

 this hypothesis is the fact that repeatedly frozen and thawed cheek 

 pouch slime will protect overlays of normal homologous skin for a long 

 time. On an enzyme hypothesis, such as that you have suggested, one 

 would have anticipated the necessity for the persistence of living 

 mesenchymal cells to maintain the protective effect. 



Krohn : Are you supposing that the slimy material of the connective 

 tissue is responsible for your effect and, if so, do you think perhaps it is 

 hyaluronic acid material ? 



Billingham: When I use the adjective "slimy" it is only in a purely 

 descriptive sense. When sectioned and studied by orthodox histological 

 methods, cheek pouch connective tissue is seen to have an abundant 

 and well differentiated fibre content. 



Krohn: Another sort of skin which does have a lot of hyaluronic acid 

 in it is the sexual skin of monkeys. When I tried to transplant pieces of 

 sexual skin with an underlying layer of this thick jelly-like slimy 

 material, the grafts did not take. 



Billingham : Were those thick grafts ? 



Krohn: They had of necessity to be thick grafts, and the epithelium 

 overlying the dermis is very thick as well, so they may not really have 

 had a chance. 



Lawrence: Is there much known about the normal immunological 

 capacity of the hamster in terms of induction and manifestations of 

 delayed allergy and serum antibody formation ? Could it be that it has 

 some central immunological deficiency, even though responding rather 

 normally to an orthotopic skin graft ? 



Billinghatn: Dr. Hildemann is more qualified to answer this than 

 I am. 



Hildemann: Hamsters respond very vigorously to a variety of hetero- 

 logous antigens. For example, the injection of a moderate dosage of rat 

 cells into the hamster will ehcit a very high titre of saline haemagglutin- 

 ins. The hamster will also make precipitins against protein antigens. 

 So I think the idea that the hamster is incompetent in any general 



