HEMATOLOGIC EFFECTS OF RADIATION 1081 



to form antibodies (anti-sheep-cell hemolysin) was compared with various 

 control groups given the same antigen at the same time relative to the 

 irradiation as the experimental animals. The capacity to form anti- 

 bodies to the injected antigen was retained in the rabbits, given 800 or 

 500 r of total-body X irradiation, which had spleen shielding during 

 irradiation and the spleen left intact in the circulation for 24 hours and 

 then removed surgically even though the antigen was given 24 hours 

 after splenectomy and 48 hours after irradiation. The fact that these 

 rabbits retained the capacity to form antibodies even though hemato- 

 poietic tissues in the body were as yet atrophic and that control rabbits 

 exposed to the same dose did not retain this capacity is considered to be a 

 result of the functional restoration of cells in the body (such as free and 

 fixed macrophages and reticular cells) by a humoral (noncellular) sub- 

 stance entering the general circulation from the originally shielded spleen 

 during the 24 hours prior to splenectomy. 



COMMENT 



It seems extremely unlikely that cell migration from the shielded or 

 transplanted tissue and subsequent proliferation of these cells account for 

 the reconstitution of hematopoietic tissues and increased survival of 

 irradiated animals or that neutralization of some toxin produced by 

 irradiation can account for these findings. Perhaps the latter possibility 

 cannot be positively excluded on the basis of the available data. The 

 evidence accumulated strongly suggests that the factor (or factors) 

 responsible for recovery from radiation under these circumstances is non- 

 cellular and may be required only for the initiation of the repair process. 

 The factor (or factors) may be quite labile or, as is more likely, may be 

 produced in an effective quantity only by living cells. These cells may be 

 present in shielded or implanted tissue or may migrate out and produce 

 the factor under discussion. The factor may be a single substance such 

 as an enzyme or coenzyme necessary for the functional reconstitution of 

 many different cell types in the several organ systems, or several different 

 factors may be concerned. Salisbury et al. (1951) found in a small 

 number of dogs that early direct cross transfusion between irradiated 

 (LD 90 , X ray) and nonirradiated dogs significantly reduced mortality, 

 reduced the severity of the expected hematopoietic depression, and 

 reduced the severity of the usual clinical signs of irradiation sickness. 

 Salisbury's experiments (1951) should be expanded in numbers of animals 

 and should be more adequately controlled to make the significance of the 

 experiment more clear cut. 



The fact that 75 per cent of mice that have lead shielding of the spleen 

 during exposure to 1025 r and then splenectomy 1 hour after the irradia- 

 tion-spleen-shielding procedure survive would lead to the expectation 

 that early administration of whole blood is effective. This seems logical 



