Related Experiment Video
Updated: Aug 9, 2026
Harvesting Murine Alveolar Macrophages and Evaluating Cellular Activation Induced by Polyanhydride Nanoparticles
Published on: June 8, 2012
Silica and PM1648 modify human alveolar macrophage antigen-presenting cell activity in vitro
R F Hamilton1, J C Pfau, G D Marshall
1University of Texas Medical School, Department of Internal Medicine, Houston, USA.
Abstract:
Some inhaled particles are known to lead to inflammation and lung pathology, whereas others do not appear to have long-term effects. Potential mechanisms to account for these differences are only beginning to be understood. In this article we examine whether silica and PM1648 (a model urban particulate) caused selective deletion of the suppressor human alveolar macrophage (HAM) phenotype (RFD1+/7+), and whether this affected cytokine production in an antigen-presenting cell (APC) assay with autologous T lymphocytes. HAM were exposed to the bioactive particulates, silica and PM1648, for 24 hours, then isolated free of extracellular particulates and nonviable cells; HAM were then cultured with autologous lymphocytes in an 11-day APC assay. Silica exposure up-regulated a TH1 lymphocyte-derived cytokine, interferon gamma (IFN-gamma), and a TH2 lymphocyte-derived cytokine, interleukin-4 (IL-4). PM1648 exposure primarily upregulated IL-4. Neither particle exposure had a significant effect on interleukin-10 (IL-10) production. Control particulate exposures with titanium dioxide (TiO2) and wollastonite (Woll) caused no altered APC activity. Silica and PM1648 demonstrated selective toxicity to suppressor macrophages (RFD1+/7+). We propose that, because of the suppressor macrophage phenotype disabling, the activator macrophage (RFD1+/7-) operates free of the suppressor macrophage's influence, enhancing APC activity with increased lymphocyte-derived proinflammatory cytokine production.
Insights
Inhaled silica and urban particulates selectively harm suppressor macrophages, increasing inflammation. This particle-induced lung inflammation results from disabling immune cell regulation.
Area of Science:
- Immunology
- Environmental Health
- Toxicology
Background:
- Inhaled particles can cause lung inflammation and pathology, but mechanisms remain unclear.
- Human alveolar macrophages (HAM) play a role in immune responses to inhaled substances.
- Specific macrophage phenotypes may influence inflammatory outcomes.
Purpose of the Study:
- To investigate if silica and PM1648 selectively eliminate suppressor HAM phenotypes (RFD1+/7+).
- To determine the effect of particle exposure on cytokine production in an antigen-presenting cell (APC) assay.
- To understand how particle-induced changes in HAM affect autologous T lymphocyte responses.
Main Methods:
- HAM were exposed to silica or PM1648 for 24 hours.
- Isolated HAM were cultured with autologous lymphocytes in an 11-day APC assay.
- Cytokine production (IFN-gamma, IL-4, IL-10) and HAM phenotype changes were analyzed.
Main Results:
- Silica exposure upregulated both IFN-gamma and IL-4; PM1648 primarily upregulated IL-4.
- Neither particle affected IL-10 production.
- Silica and PM1648 selectively eliminated suppressor HAM (RFD1+/7+), while control particles (TiO2, Woll) did not.
Conclusions:
- Exposure to silica and PM1648 induces selective toxicity towards suppressor macrophages.
- Disabling of suppressor macrophages by these particles enhances APC activity.
- This leads to increased production of pro-inflammatory cytokines, contributing to lung inflammation.
