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Updated: May 1, 2026
Characterization of Immune Cells and Proinflammatory Mediators in the Pulmonary Environment
Published on: June 24, 2020
Functional characterisation of human pulmonary monocyte-like cells in lipopolysaccharide-mediated acute lung
Mairi Brittan1, Laura C Barr2, Niall Anderson3
1BHF/University Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK ; BHF Centre for Cardiovascular Science, Scottish Centre for Regenerative Medicine, The University of Edinburgh, 5 Little France Drive, Edinburgh EH16 4UU, UK.
Background:
We have previously reported the presence of novel subpopulations of pulmonary monocyte-like cells (PMLC) in the human lung; resident PMLC (rPMLC, HLA-DR(+)CD14(++)CD16(+)cells) and inducible PMLC (iPMLC, HLA-DR(+)CD14(++)CD16(-) cells). iPMLC are significantly increased in bronchoalveolar lavage (BAL) fluid following inhalation of lipopolysaccharide (LPS). We have carried out the first functional evaluation of PMLC subpopulations in the inflamed lung, following the isolation of these cells, and other lineages, from BAL fluid using novel and complex protocols.
Methods:
iPMLC, rPMLC, alveolar macrophages (AM), neutrophils, and regulatory T cells were quantified in BAL fluid of healthy subjects at 9 hours post-LPS inhalation (n = 15). Cell surface antigen expression by iPMLC, rPMLC and AM and the ability of each lineage to proliferate and to undergo phagocytosis were investigated using flow cytometry. Basal cytokine production by iPMLC compared to AM following their isolation from BAL fluid and the responsiveness of both cell types following in vitro treatment with the synthetic corticosteroid dexamethasone were assessed.
Results:
rPMLC have a significantly increased expression of mature macrophage markers and of the proliferation antigen Ki67, compared to iPMLC. Our cytokine data revealed a pro-inflammatory, corticosteroid-resistant phenotype of iPMLC in this model.
Conclusions:
These data emphasise the presence of functionally distinct subpopulations of the monocyte/macrophage lineage in the human lung in experimental acute lung inflammation.
Insights
Novel pulmonary monocyte-like cells (PMLC) were functionally evaluated in the inflamed human lung. Inducible PMLC (iPMLC) show a pro-inflammatory, corticosteroid-resistant phenotype, distinct from resident PMLC (rPMLC).
Area of Science:
- Immunology
- Pulmonary Medicine
- Cell Biology
Background:
- Novel pulmonary monocyte-like cells (PMLC) include resident (rPMLC) and inducible (iPMLC) subpopulations.
- iPMLC increase in bronchoalveolar lavage (BAL) fluid after lipopolysaccharide (LPS) inhalation.
- This study provides the first functional evaluation of PMLC subpopulations in an inflamed lung model.
Purpose of the Study:
- To functionally characterize distinct pulmonary monocyte-like cell (PMLC) subpopulations.
- To compare the inflammatory and phagocytic capacities of resident PMLC (rPMLC) and inducible PMLC (iPMLC).
- To assess the corticosteroid responsiveness of these cell types in acute lung inflammation.
Main Methods:
- Quantification of iPMLC, rPMLC, alveolar macrophages (AM), neutrophils, and regulatory T cells in BAL fluid post-LPS inhalation.
- Flow cytometry analysis of cell surface antigens, proliferation, and phagocytosis.
- Assessment of basal and dexamethasone-induced cytokine production by iPMLC and AM.
Main Results:
- Resident PMLC (rPMLC) exhibit higher expression of mature macrophage markers and Ki67 compared to inducible PMLC (iPMLC).
- Inducible PMLC (iPMLC) demonstrate a pro-inflammatory cytokine profile.
- iPMLC display resistance to corticosteroid treatment in vitro.
Conclusions:
- Pulmonary monocyte-like cell (PMLC) subpopulations are functionally distinct in the human lung during acute inflammation.
- Inducible PMLC (iPMLC) contribute to inflammation and are resistant to corticosteroids.
- These findings highlight the heterogeneity of the monocyte/macrophage lineage in lung inflammation.
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