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Absence of CSF-1 in macrophage-deficient op/op mice has differential effects on macrophage colony stimulating
W Wiktor-Jedrzejczak1, K W Sell, P Szwech
1Department of Immunology, Military School of Medicine, Warsaw, Poland.
Abstract:
The absence of detectable levels of CSF-1 in op/op mice results in a marked deficiency of macrophage colony-stimulating activity (M-CSA) in both the unstimulated and postendotoxin sera of these animals. These deficiences are not secondary to the presence of an inhibitor of macrophage formation. In contrast, various organs, particularly the organs of endotoxin-treated op/op mice, released amounts of M-CSA comparable to those of normal mice. Similarly, mitogen-stimulated lymphoid cells from op/op mice released either similar or increased amounts of M-CSA compared to mitogen stimulated +/+ lymphoid cells. On the other hand, conditioned media from cultures of fibroblastoid cells obtained from primary and secondary cultures of op/op organs were nearly totally devoid of M-CSA. However, incubation of these op/op fibroblasts with endotoxin in vitro induced the easily and readily detectable levels of M-CSA. These data suggest that CSF-1 is most likely a major source of M-CSA in serum and postendotoxin serum, while its contribution to soluble M-CSA in other organs may be only partial. In addition, in specific circumstances, the induced release of other macrophage growth factors may partially compensate for CSF-1 deficiency. Furthermore, it appears that the generalized macrophage deficiency in op/op mice cannot be fully explained by the deficiency of soluble M-CSA (soluble CSF-1) and argues for an in vivo role of membrane-bound CSF-1. These data may be interpreted as supporting a model in which the regulation of CSF-1-dependent and CSF-1-independent macrophage production is carried out by partly unrelated mechanisms.
Insights
Colony-stimulating factor-1 (CSF-1) deficiency in op/op mice impairs macrophage activity. However, other factors and membrane-bound CSF-1 may compensate, suggesting complex macrophage regulation.
Area of Science:
- Immunology
- Hematopoiesis
- Cell Biology
Background:
- op/op mice exhibit a deficiency in macrophage colony-stimulating activity (M-CSA).
- This deficiency is linked to absent detectable levels of colony-stimulating factor-1 (CSF-1).
- The study investigates the source and regulation of M-CSA in CSF-1 deficient mice.
Purpose of the Study:
- To determine the role of CSF-1 in M-CSA production in serum and organs.
- To investigate compensatory mechanisms for CSF-1 deficiency in macrophage production.
- To explore the in vivo significance of membrane-bound CSF-1.
Main Methods:
- Assessing M-CSA levels in sera and organ extracts of op/op and normal mice.
- Culturing fibroblastoid cells from op/op mice and stimulating them with endotoxin in vitro.
- Analyzing M-CSA release from mitogen-stimulated lymphoid cells.
Main Results:
- op/op mice showed deficient M-CSA in sera, but organs released comparable M-CSA levels, especially after endotoxin treatment.
- Fibroblastoid cells from op/op mice produced minimal M-CSA, but endotoxin induced detectable levels in vitro.
- CSF-1 appears to be a major source of serum M-CSA, with partial contributions in other organs.
- Other macrophage growth factors and membrane-bound CSF-1 may compensate for CSF-1 deficiency.
Conclusions:
- CSF-1 is a primary source of serum M-CSA, but not the sole contributor to M-CSA in all tissues.
- Induced release of other factors and membrane-bound CSF-1 suggest complex, multifactorial regulation of macrophage production.
- The generalized macrophage deficiency in op/op mice highlights the importance of both soluble and membrane-bound CSF-1 in vivo.