Effect of colony-stimulating factor-producing tumor on hemopoiesis in splenectomized mice

The colony-stimulating factor-producing BMA-1 tumor was transplanted into splenectomized mice. These mice showed as much granulocytosis as non-splenectomized mice bearing the tumor. The increase in the number of peripheral leukocytes induced per tumor weight was similar in the two groups. The hemopoietic cell population in the central bone marrow (tibia) was not increased by splenectomy. The total numbers of spleen colony-forming cells and granulocyte-macrophage colony-forming cells in the whole body of tumor-bearing splenectomized mice were 29% and 58% of those in the tumor-bearing non-splenectomized mice, respectively. The expansion of hemopoiesis to the peripheral bone marrow in tumor-bearing splenectomized mice was confirmed by histological examination of the tail bone. These results suggest that the lack of increase in the bone marrow cellularity is due to the space limitation, and that this is well compensated for by a great expansion of hemopoietic marrow to the peripheral bones in splenectomized mice.