Lack of correlation between splenic and marrow hematopoiesis following irradiation or irradiation and transplantation in mice.

Differences were seen in the relative importance of spleen and marrow in early erythroid regeneration of lethally irradiated mice given spleen or marrow cell transplants compared with that in sublethally irradiated mice with surviving endogenous hematopoietic cells. Radioactive iron uptake was predominantly in the spleen of mice with transplants and in the marrow of endogenously recovering mice. Visable spleen colony counts increased from day 4 to day 7 and plateaued through day 10 in the transplant system, but shoed a small abortive rise with a 5-day peak, followed by a steady increase from days 6 to 10 in the endogenous system. Comparisons of peroxidase-positive cells (granulocytes) in the marrow of femurs and humeri and iron uptake in marrow and spleen suggested that repopulation of the marrow and spleen were independent, while that of different areas of the marrow was interrelated. The interrelationship of the rate of marrow regeneration was closer in the endogenous than in the transplant system.