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Updated: Nov 3, 2025
An In vitro Model to Study Heterogeneity of Human Macrophage Differentiation and Polarization
Published on: June 12, 2013
Phenotypic and Functional Heterogeneity of Low-Density and High-Density Human Lung Macrophages
Barbara Balestrieri1, Francescopaolo Granata1,2, Stefania Loffredo1,2,3,4
1Department of Translational Medical Sciences, University of Naples Federico II, 80131 Naples, Italy.
Background:
Pulmonary macrophages are a highly heterogeneous cell population distributed in different lung compartments.
Methods:
We separated two subpopulations of macrophages from human lung parenchyma according to flotation over density gradients.
Results:
Two-thirds 65.4% of the lung macrophages have a density between 1.065 and 1.078 (high-density macrophages: HDMs), and the remaining one-third (34.6) had a density between 1.039 and 1.052 (low-density macrophages: LDMs). LDMs had a larger area (691 vs. 462 μm2) and cell perimeter (94 vs. 77 μm) compared to HDMs. A significantly higher percentage of HDMs expressed CD40, CD45, and CD86 compared to LDMs. In contrast, a higher percentage of LDMs expressed the activation markers CD63 and CD64. The release of TNF-α, IL-6, IL-10 and IL-12 induced by lipopolysaccharide (LPS) was significantly higher in HDMs than in LDMs.
Conclusion:
The human lung contains two subpopulations of macrophages that differ in buoyancy, morphometric parameters, surface marker expression and response to LPS. These subpopulations of macrophages probably play distinct roles in lung inflammation and immune responses.
Insights
Human lungs contain two distinct pulmonary macrophage subpopulations: high-density (HDMs) and low-density (LDMs). These macrophages differ in size, surface markers, and inflammatory response, suggesting unique roles in lung immunity.
Area of Science:
- Immunology
- Cell Biology
- Pulmonary Medicine
Background:
- Pulmonary macrophages are key immune cells in the lungs, exhibiting significant heterogeneity.
- Their distribution across different lung compartments contributes to diverse functions.
Purpose of the Study:
- To investigate and characterize distinct subpopulations of human lung macrophages.
- To identify differences in their physical properties, surface markers, and inflammatory responses.
Main Methods:
- Human lung parenchyma macrophages were isolated using density gradient centrifugation.
- Subpopulations were analyzed for morphometric parameters, surface marker expression (CD40, CD45, CD86, CD63, CD64), and cytokine release (TNF-α, IL-6, IL-10, IL-12) upon LPS stimulation.
Main Results:
- Two macrophage subpopulations were identified: high-density macrophages (HDMs, 65.4%) and low-density macrophages (LDMs, 34.6%).
- LDMs were larger with greater cell perimeter than HDMs.
- HDMs showed higher expression of CD40, CD45, and CD86, while LDMs expressed more CD63 and CD64. HDMs released significantly higher levels of TNF-α, IL-6, IL-10, and IL-12 in response to LPS compared to LDMs.
Conclusions:
- Human lungs harbor at least two distinct macrophage subpopulations with differing density, morphology, surface markers, and inflammatory responses.
- These macrophage subsets likely fulfill specialized roles in lung inflammation and immune regulation.
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