DISCUSSION 



adult lymph-node, in each case there being a considerable contribution of mature 

 lymphoid tissue, then the animals do not survive for more than a few weeks, and 

 usually they die in the first ten days or so and the death therefore is contemporary with 

 the radiation syndrome. Your type of experiment obviously is better designed to 

 elucidate this particular point, because the radiation dose is not sufficient to cause 

 the death of the animal by itself and any delayed death is therefore probably largely 

 contributed to by this reaction of the grafted spleen against the host. Certainly, if 

 we give bone marrow to restore lethally irradiated mouse and homologous lymphoid 

 tissue, adult lymphoid tissue which has been made immune against the host-type 

 material, then we do get death within about five or six days ; that is even before the 

 irradiation syndrome manifests itself in complete form, and in those cases the lymph- 

 oid tissues of the chimacra are stuffed with large basophilic cells which could be 

 these antibody producing type cells, although we have not made any formal tests 

 for the type of antibodies they are producing. I think the important thing is, with 

 all these things, that we can produce a reaction of the graft against the host, but we 

 have not yet found a means of turning it off at will. 



Dr. Vogel : I wonder, Dr. Loutit, if you have tried any experiments of a similar 

 nature following neutron irradiation. The reason I ask is that there is just a tendency 

 of an indication in some works that we have done, that although we got secondary 

 homologous deaths after y-rays, after neutrons we do not seem to. 



Dr. Loutit : We ourselves have not done any work, but I am aware that work has 

 been published, both from Oak Ridge and San Francisco on this point, but off-hand 

 I cannot recall that this was on homologously treated neutron-irradiated animals, 

 and therefore I cannot recall in those reports, whether there was evidence of this 

 'secondary disease' or not. Can you remember? 



Dr. Vogel : Yes, I believe they were all isologous. 



Dr. Loutit: That is my impression, yes. In which case one would not expect to see 

 this delayed death, and I am very interested to hear your observation on this point 

 and would like to discuss it afterwards. 



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