Related Experiment Videos
Mast cells and macrophages in normal C57/BL/6 mice
Christine Gersch1, Oliver Dewald, Martin Zoerlein
1Section of Cardiovascular Sciences, Baylor College of Medicine, One Baylor Plaza M/S F-602, Houston TX 77030, USA.
Insights
Mast cells and macrophages show varied distribution in mouse tissues, with stem cell factor (SCF) and macrophage colony-stimulating factor (M-CSF) mRNA expression not always correlating with cell presence, suggesting broader roles in tissue homeostasis.
Area of Science:
- Immunology
- Cell Biology
- Tissue Distribution Studies
Background:
- Mast cells and macrophages are key immune cells involved in inflammation.
- Mice are critical models for studying immune and inflammatory responses.
- Understanding immune cell distribution is vital for interpreting experimental findings.
Purpose of the Study:
- To map the distribution of mast cells and macrophages in normal mouse tissues.
- To investigate the mRNA expression of key growth factors (SCF, M-CSF, GM-CSF) in these tissues.
- To explore potential correlations between growth factor expression and immune cell populations.
Main Methods:
- Histochemical and immunohistochemical staining for mast cells and macrophages (using F4/80 antibody).
- Nuclease protection assay to quantify mRNA expression of stem cell factor (SCF), macrophage colony-stimulating factor (M-CSF), and granulocyte macrophage colony-stimulating factor (GM-CSF).
- Comparative analysis of cell distribution and growth factor mRNA levels across various murine organs.
Main Results:
- Mast cells were abundant in the dermis, tongue, and skeletal muscle, but scarce in organs like the heart and spleen.
- Macrophages were prevalent in the spleen, lung, liver, kidney, and bowel, with low numbers in the heart and dermis.
- SCF mRNA was high in the lung but low in mast cell-rich tongue and earlobe; M-CSF and GM-CSF mRNA were high in the lung and spleen; the heart showed high M-CSF but low GM-CSF mRNA.
Conclusions:
- Murine mast cell and macrophage distribution varies significantly across different tissue types.
- Growth factor mRNA expression patterns do not consistently align with the local abundance of mast cells and macrophages.
- Constitutive expression of growth factors in tissues with low immune cell populations may indicate roles beyond cell survival and proliferation, potentially in tissue homeostasis.
Abstract:
Mast cells and macrophages have an important role in immunity and inflammation. Because mice are used extensively for experimental studies investigating immunological and inflammatory responses, we examined mast cell and macrophage distribution in normal murine tissues. Mast cells were abundant in the murine dermis, tongue, and skeletal muscle but were rarely found in the heart, lung, spleen, kidney, liver, and the bowel mucosa. In contrast, dogs exhibited large numbers of mast cells in the lung parenchyma, liver, and bowel. Some murine dermal mast cells had long cytoplasmic projections filled with granular content. Mouse mast cells demonstrated intense histamine immunoreactivity and were identified with histochemical enzymatic techniques for tryptase and chymase. Macrophages, identified using the monoclonal antibody F4/80, were abundant in the spleen, lung, liver, kidney, and bowel but relatively rare in the heart, tongue, and dermis. Using a nuclease protection assay we investigated mRNA expression of stem cell factor (SCF), a crucial survival factor for mast cells, and the macrophage growth factors macrophage colony stimulating factor (M-CSF) and granulocyte macrophage colony stimulating factor (GM-CSF). Stem cell factor mRNA was highly expressed in the murine lung. Relatively low levels of SCF mRNA expression were found in the tongue and earlobe, which are tissues containing a high number of mast cells. Macrophage CSF and GM-CSF mRNA was highly expressed in the lung and spleen. The murine heart, an organ with a low macrophage content, expressed high levels of M-CSF but negligible levels of GM-CSF mRNA. Constitutive growth factor mRNA expression in murine tissues without significant populations of mast cells and macrophages may suggest an alternative role for these factors in tissue homeostasis.