DISCUSSION 



We have tried to repeat his work but have been unable to obtain significant 

 survival when morphologically intact cells were absent fi^om the injection 

 preparation. In fact, we have been unable to produce a preparation, using 

 Cole's technique, that was entirely cell-free. Approaching the problem 

 from another point of view, we have attempted to learn whether Cole's 

 technique would destroy or limit the capacity of leukaemic cells to induce 

 leukaemia in normal or irradiated mice^. Thus far, we have found that these 

 preparations produce leukaemia in the recipient mice. Many morpho- 

 logically intact cells were found present in the injection material and their 

 leukaemia-inducing capacity was obviously not affected. 



SUMMARY AND CONCLUSIONS 



Nucleated cells derived from various tissues of the haematopoietic system of 

 normal adult, baby, and embryonic mice and suspended in saline or Locke's 

 solution have been prepared and injected into irradiated mice. These 

 preparations were standardized in terms of the number of nucleated cells 

 per 0-5 cm3 of suspension fluid (range, 0-05 X 10" to 88 X 10") in order to 

 make comparisons of the effects of the number of cells and their source on 

 the enhancement of survival of irradiated recipients. The data indicate 

 that fewer cells are required in suspensions made from young mice than from 

 adult donors. The sources from which the cells were derived were unim- 

 portant. Sixty-three per cent of the mice irradiated with 900 r survived 

 following the injection of about 3x10*^ cells from young donors as compared 

 with 23 per cent survival when the recipients were injected with the same 

 number of bone marrow cells from adult donors. With 750 r, only 150,000 

 marrow cells from 4- to 5-week old mice were required to enhance survival. 

 Bone marrow obtained from donor mice irradiated with 100 or 200 r one day 

 before removal of the bone marrow cells is effective ; whereas that from mice 

 exposed to 400 r or more is ineffective in enhancing the survival of mice 

 exposed to 900 r. 



REFERENCES 



1 Jacobson, L. O., Marks, E. K., Gaston, E. O., Robson, M. J. and Zirkle, R. E. 

 Proc. Soc. Expt. Biol. Med. 1949, 70 740. 



2 Jacobson, L. O. Cancer Res. 1952, 12 315. 



3 Cole, L. J., Fishler, M. C, Ellis, M. E. and Bond, V. P. Proc. Soc. Expt. Biol. 

 Med. 1952.80 112. 



* Lorenz, E., Congdon, C. C. and Uphoff, D. Radiology, 1952, 58 863. 



s Jacobson, L. O., Simmons, E. L., Marks, E. K. and Eldredge, J. H. Science, 



1951,113 510. 

 " Simmons, E. L., Goldwasser, E. and Jacobson, L. O. Manuscript in preparation. 



DISCUSSION 



L. J. Cole : I think it should be pointed out, relative to the data of Jacobson 

 et al, that their spleen cell suspensions were administered by intravenous injection ; 

 in our own studies, the spleen nuclei fraction preparations were routinely adminis- 

 tered intraperitoneally. The former route of administration is far less efficient than 

 the latter, e.g. less material is required for the same level of protection. Thus, we 

 have found that the intravenous injection of spleen nuclei fraction, derived from the 

 equivalent of 0-75 spleen, will provide the same degree of protection against 750 r 

 (whole-body X-irradiation) as the nuclei fraction equivalent to 5 spleens, when 

 injected intraperitoneallv. 



133 



