Incubation with high doses of tritiated thymidine in vitro was used to determine the percent of progenitor cells in the S phase of the cell cycle. Peripheral blood (PB), bone marrow (BM), and spleen populations from mice injected with granulocyte colony-stimulating factor (G-CSF) at 5 micrograms/day for 5 days and BM cells from uninjected littermates were assayed. Although the percentage of pro...

The concentration of the macrophage-specific colony-stimulating factor (CSF-1) and the numbers of bone marrow and spleen cells with specific receptors for that factor have been investigated in a number of mouse strains under normal conditions and after infection with the facultative intracellular bacterium Listeria monocytogenes. The CSF-1 concentration in serum and tissue was markedly elevated...

A factor able to stimulate the proliferation and differentiation of multipotential stem cells and progenitor cells of the granulocyte-macrophage, eosinophil, and erythroid lineages as well as being able to maintain factor-dependent cell lines in culture has been purified from pokeweed mitogen-stimulated mouse spleen cell-conditioned medium. The factor was purified over 2 million-fold by sequent...

Acidic isoferritins have been identified as leukemia-associated inhibitory activity (LIA), which suppresses colony and cluster formation of colony-forming unit-granulocyte macrophages from normal donors but not from patients with leukemia. LIA was detected in all ferritin preparations tested, including ferritin isolated from normal heart, spleen, liver, and placental tissues, and from the splee...

The proto-oncogene c-kit encodes a transmembrane tyrosine kinase receptor for stem cell factor (SCF). The c-kit/SCF signal is expected to have an important role in hematopoiesis. A monoclonal antibody (ACK-2) against the murine c-kit molecule was prepared. Flow cytometric analysis showed that the bone marrow cells that expressed the c-kit molecule (approximately 5%) were B220(B)-, TER119(erythr...

Hematopoiesis is thought to be modulated by interactions of progenitor cells with hematopoietic growth factors. We have shown that colony-forming units-spleen (CFU-S) and repopulating stem cells require interleukin-3 (IL-3) to survive in vitro, and that CFU-S number and long-term repopulating ability can be increased by culture in the combination of IL-3 and IL-6. In this report, we describe th...

Very high concentrations of erythropoietin (epo), in clonogenic cultures, result in reduced production of neutrophils, and fetal progenitors are more sensitive to this effect of epo than are those of adults. However, the significance of this observation is unclear because no evidence of reduced neutrophil production has been presented following administration of recombinant epo to human or anim...

In a study of the components of antiserum prepared (in S I M / M c K mice) against formalinized Friend leukemic cell suspensions, the spleen focus assay method was employed for measuring the kinetics of virus neutralization, and the spleen colony method was used to monitor the loss of tumor colonyforming ability during the cytotoxic reaction. Repeated absorption of Friend antiserum with resuspe...

Friend spleen focus-forming virus (F-SFFV) is a replicationdefective retrovirus that induces a multistage erythroleukemia in mice. In the first stage, expression of the SFFV envelope glycoprotein results in erythroid hyperplasia. Subsequently, the F-SFFV integrates near the Spi-1 gene and activates its expression, resulting in immortalized cells that represent a second stage in the disease proc...

Spleen organ cultures were prepared from lethally irradiated mice that had been injected with allogeneic bone marrow, with or without lymph node cells. These cultures were used in the analysis of graft-versus-host reactions (GVHR) in vitro. It was found that donor-derived T lymphocytes, which had been grown in an allogeneic spleen, prevented hemopoietic progenitor cells (colony-forming cells, C...