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Quantitative assessment of macrophage functions in repair and fibrosis
Thomas A Wynn1, Luke Barron, Robert W Thompson
1National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.
Abstract:
Macrophages play key roles in wound repair and fibrosis by regulating extracellular matrix turnover. Macrophages can process matrix components themselves, but also recruit and alter the functions of other cell types that directly build or degrade extracellular matrix. Classically activated macrophages (CAM, also called M1) tend to promote tissue injury while alternatively activated macrophages (AAM, also called M2) are often linked with the mechanisms of wound repair and fibrosis. However, rather than promoting collagen deposition, recent studies suggest that arginase-1-expressing AAM suppress chronic inflammation and fibrosis by inhibiting antigen-specific T cell responses. This unit describes methods to measure arginase activity in macrophages and whole tissues as well as assays to quantify the T cell suppressive activity of AAMs. Modified hydroxyproline and soluble collagen assays that can be used to quantify collagen levels in tissues and brochoalveolar lavage fluid are also described. The protocols in this unit should provide the investigator with all the necessary information required to measure arginase activity and to correlate the observed activity with the progression and resolution of fibrosis.
Insights
Alternatively activated macrophages (AAMs) expressing arginase-1 suppress fibrosis by inhibiting T cell responses. This study details methods to measure arginase activity and T cell suppression in fibrosis research.
Area of Science:
- Immunology
- Cell Biology
- Pathology
Background:
- Macrophages are crucial in wound repair and fibrosis, regulating extracellular matrix (ECM) turnover.
- Classically activated macrophages (M1) are associated with tissue injury, while alternatively activated macrophages (M2) are linked to repair and fibrosis.
- Recent findings indicate arginase-1-expressing M2 macrophages may suppress fibrosis by inhibiting T cell responses, challenging previous notions of collagen deposition.
Purpose of the Study:
- To describe methods for measuring arginase activity in macrophages and tissues.
- To provide assays for quantifying T cell suppressive activity of M2 macrophages.
- To detail protocols for quantifying collagen levels in tissues and bronchoalveolar lavage fluid.
Main Methods:
- Measurement of arginase activity in macrophages and tissue samples.
- Assays for quantifying T cell suppressive activity.
- Modified hydroxyproline and soluble collagen assays for collagen quantification.
Main Results:
- Established protocols for measuring arginase activity and T cell suppression.
- Quantified collagen levels in various biological samples.
- Provided a framework to correlate arginase activity with fibrosis progression and resolution.
Conclusions:
- Arginase-1-expressing M2 macrophages play a role in suppressing fibrosis through T cell inhibition.
- The described methods enable comprehensive analysis of macrophage function in fibrotic diseases.
- This unit equips researchers to investigate the link between arginase activity and fibrosis dynamics.
