OBSERVATIONS ON THE EFFECT OF SPLEEN-SHIELDING 



In the original work by Jacobson et al^ in which splenic implants were 

 found to enhance survival, four spleens from baby mice were required to 

 effect increased survival of adult irradiated mice. When spleen-cell sus- 

 pensions were injected intravenously, however, the cells from only one spleen 

 were sufficient to enhance survival in several irradiated mice. To correlate 

 the results of these studies with those from bone marrow experiments, cell 

 counts were made on the spleen-cell suspensions. When 8 to 11 x 10^ 

 nucleated cells from the spleens of 2-day mice were given intravenously, 

 70 per cent of the recipients survived the 28-day period of observation, with 

 no deaths occurring before the 18th day after irradiation ; with 3 to 5 X 10^ 

 cells, 7 of 12 or 58 per cent survived ; with 2 to 3 X 10^ nucleated cells, 

 8 of 1 1 or 71 per cent survived ; and with as few as 0-5 to 0-75 X 10^ cells, 

 70 per cent survived. As indicated in Table III, survival was generally in the 

 range of 50 to 70 per cent regardless of the total number of cells injected. 



Cells obtained from adult spleen have thus far proved to be less effective 

 than cells from the spleens of younger mice. Instantaneous deaths were 

 frequent after the intravenous administration of cell suspensions containing 

 10 X 10^ or more cells*. This toxic action can be overcome to a great 

 extent if the adult spleen cells are washed thoroughly by centrifugation in 

 Locke's solution and if a few drops of heparin are added to the suspension 

 made from the washed cells just prior to injection. The data in Table IV 

 provide a comparison of the effectiveness of spleen cells obtained from mice 

 aged 2 days, 4 to 6 weeks, and 10 to 12 weeks. In the latter group, the effect 

 of washing the cells and the addition of heparin are also shown. 



Although spleen cells from adult mice had little, if any, effect on the 

 survival of mice when 8 to 11 X 10® cells were given, 26 per cent of the 

 irradiated recipients survived when 50 to 60 X 10® cells were injected intra- 

 venously. The addition of heparin did not influence the 28-day survival. 



The effect of embryo cells on survival of mice — Since earlier studies showed that 

 35 per cent of mice survived when embryo mash was given intraperitoneally 

 following a lethal exposure to X-radiation (1025r) and since less than 

 1 X 10® nucleated cells from 2-day mouse spleens were necessary to 

 enhance survival, an effort has been made to determine the number of 

 embryo cells that are necessary to bring about this protective action. 



Suspensions that were made from cells obtained by pressing the entire 

 embryo through a tissue press or by grinding it in a mortar inevitably proved 

 fatal to the irradiated recipient, which was injected intravenously. Portions 

 of the soft tissue of the embryo (mostly liver) were tested. Suspensions from 

 this tissue were made with Locke's solution and were given intravenously 

 after irradiation. 



With 10 to 88 X 10® cells, 46-8 per cent of the mice survived 900 r. Fifty 

 per cent survived with as few as 1 to 3 X 10® cells, and 26 per cent survived 

 with 0-3 to 1-0 X 10® cells. With such a small amount as 0-1 to 0-3 X 10® 

 embryo (liver) cells, 25 per cent survived 900 r {Table V). 



The comparative effectiveness of various tissue-cell suspensions is shown 

 in Table VI. The data indicate that 5-0 to 10-0 x 10® cells per mouse are 



* Considerable difficulty is encountered when heparin is added to the suspension before 

 the cells are counted since clumping of the white cells under these conditions is marked and 

 accurate counts cannot be made. 



126 



