Related Experiment Video
Updated: Jul 4, 2026
In Vivo Assessment of Alveolar Macrophage Efferocytosis Following Ozone Exposure
Published on: October 22, 2019
Depletion of resident alveolar macrophages does not prevent Fas-mediated lung injury in mice
1Research Service of the Veterans Affairs Puget Sound Health Care System, University of Washington, Seattle, Washington, USA.
Abstract:
Activation of the Fas/Fas ligand (FasL) system in the lungs results in a form of injury characterized by alveolar epithelial apoptosis and neutrophilic inflammation. Studies in vitro show that Fas activation induces apoptosis in alveolar epithelial cells and cytokine production in alveolar macrophages. The main goal of this study was to determine the contribution of alveolar macrophages to Fas-induced lung inflammation in mice, by depleting alveolar macrophages using clodronate-containing liposomes. Liposomes containing clodronate or PBS were instilled by intratracheal instillation. After 24 h, the mice received intratracheal instillations of the Fas-activating monoclonal antibody Jo2 or an isotype control antibody and were studied 18 h later. The Jo2 MAb induced increases in bronchoalveolar lavage fluid (BALF) total neutrophils, lung caspase-3 activity, and BALF total protein and worsened histological lung injury in the macrophage-depleted mice. Studies in vitro showed that Fas activation induced the release of the cytokine KC in a mouse lung epithelial cell line, MLE-12. These results suggest that the lung inflammatory response to Fas activation is not primarily dependent on resident alveolar macrophages and may instead depend on cytokine release by alveolar epithelial cells.
Insights
Fas activation causes lung injury, but removing alveolar macrophages did not worsen this inflammation. Lung epithelial cells, not macrophages, may drive the inflammatory response to FasL.
Area of Science:
- Immunology
- Pulmonary Medicine
- Cell Biology
Background:
- The Fas/Fas ligand (FasL) system mediates apoptosis and inflammation in the lungs.
- Alveolar macrophages are implicated in Fas-induced lung injury through in vitro studies.
Purpose of the Study:
- To investigate the role of alveolar macrophages in Fas-induced lung inflammation in vivo.
- To determine if depleting alveolar macrophages exacerbates Fas-mediated lung injury.
Main Methods:
- Mice underwent intratracheal instillation of clodronate liposomes to deplete alveolar macrophages.
- Fas-activating monoclonal antibody Jo2 or isotype control was administered intratracheally.
- Bronchoalveolar lavage fluid (BALF), lung caspase-3 activity, protein levels, and histology were analyzed.
Main Results:
- Jo2 antibody administration increased neutrophils, caspase-3 activity, and protein in BALF, and worsened lung injury.
- Macrophage depletion did not exacerbate these Jo2-induced inflammatory markers or lung injury.
- In vitro, Fas activation stimulated cytokine KC release from mouse lung epithelial cells (MLE-12).
Conclusions:
- Alveolar macrophages are not the primary drivers of Fas-induced lung inflammation.
- Alveolar epithelial cells may be a key source of cytokines, such as KC, in response to Fas activation.
- The inflammatory response to Fas activation in the lungs may not be primarily dependent on resident alveolar macrophages.
