Effects on spleen colony-forming unit self-renewal after retroviral-mediated gene transfer of multi-colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, or granulocyte colony-stimulating factor.

C57BL/6 mice were established to constitutively produce multi-colony-stimulating factor (multi-CSF), granulocyte-macrophage colony-stimulating factor, or granulocyte colony-stimulating factor by transplantation with post-5-fluorouracil-treated syngeneic marrow cells infected with retroviral vectors bearing the corresponding growth factor complementary DNAs. At 2-4 weeks after transplantation, these mice had a 2-7-fold increase in spleen colony-forming unit (CFU-S) numbers when compared to control animals transplanted with MPZipNeo-infected marrow cells. Most of the CFU-S in the former animals were located in the spleen, whereas those of control mice were found in the marrow. The increase in total CFU-S content in recipients of CSF-infected mice was not due to an increase in self-renewal ability but rather to the recruitment of more primitive cells, as there were no differences in CFU-S content of spleen colonies generated from marrow cells of either group. Neither were there any differences in the cellular composition of these spleen colonies or in the size or distribution of cell types in secondary spleen colonies generated from these spleen colonies, suggesting the inability of any of the three CSFs to alter the differentiation pattern of CFU-S.