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In vivo hematologic effects of recombinant human macrophage colony-stimulating factor
T R Ulich1, J del Castillo, L R Watson
1Department of Pathology, University of California, Irvine 92717.
Abstract:
Macrophage colony-stimulating factor (recombinant human M-CSF) given as a single intravenous injection to Lewis rats induces a dose-dependent peripheral monocytosis, neutrophilia, and lymphopenia. The monocytosis peaks at 28 to 32 hours with a seven- to eightfold increase in the number of circulating monocytes and promonocytes. The peripheral monocytosis is accompanied by a slight increase in marrow blasts, promonocytes, and monocytes. A monocytopenia reaching a nadir at 15 minutes precedes the monocytosis, suggesting that M-CSF activates circulating monocytes and causes intravascular margination. The M-CSF-induced neutrophilia and lymphopenia are relatively mild in magnitude, are observed between 2 and 16 hours after injection, and are no longer evident at later time-points. The monocytosis was at least partially inhibited by dexamethasone. M-CSF-induced monocytosis most likely reflects a direct effect of M-CSF on marrow monocyte precursor proliferation, maturation, and release, whereas the neutrophilia and lymphopenia may reflect indirect effects mediated by the known ability of M-CSF to cause the release of other cytokines.
Insights
Recombinant human macrophage colony-stimulating factor (M-CSF) injection causes a significant increase in monocytes (monocytosis) in rats. This M-CSF effect on monocytes was partially blocked by dexamethasone.
Area of Science:
- Hematology
- Immunology
- Pharmacology
Background:
- Macrophage colony-stimulating factor (M-CSF) is a key cytokine regulating myeloid cell development.
- Understanding M-CSF's in vivo effects is crucial for developing therapies targeting myeloid cell populations.
Purpose of the Study:
- To investigate the hematological effects of recombinant human M-CSF in Lewis rats.
- To characterize the dose-dependent changes in peripheral blood cell counts following M-CSF administration.
Main Methods:
- Lewis rats received single intravenous injections of varying doses of recombinant human M-CSF.
- Peripheral blood cell counts were analyzed at multiple time points post-injection.
- The effect of dexamethasone on M-CSF-induced changes was assessed.
Main Results:
- M-CSF induced a dose-dependent peripheral monocytosis, peaking at 28-32 hours with a 7-8 fold increase in monocytes and promonocytes.
- A transient monocytopenia preceded the monocytosis, suggesting margination.
- Mild, transient neutrophilia and lymphopenia were observed, likely due to indirect cytokine release.
- Dexamethasone partially inhibited the M-CSF-induced monocytosis.
Conclusions:
- M-CSF directly stimulates monocyte precursor proliferation, maturation, and release from the bone marrow.
- Neutrophilia and lymphopenia are likely indirect consequences of M-CSF's broader cytokine-releasing effects.
- M-CSF's hematological impact can be modulated by other agents like dexamethasone.