Morphologic characterization of alveolar macrophages from subjects with occupational exposure to inorganic particles

Our plain-English summary of Morphologic characterization of alveolar macrophages from subjects with occupational exposure to inorganic particles, by T. Takemura, W.N. Rom, V.J. Ferrans, et al (The American Review of Respiratory Disease, 1989).

The study

• Authors: T. Takemura, W.N. Rom, V.J. Ferrans, R.G. Crystal
• Journal: The American Review of Respiratory Disease
• Published: 1989;140(6):1674-85
• Cited by: 58 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Alveolar macrophages recovered by bronchoalveolar lavage from 43 nonsmoking or greater than 5-yr ex-smoking subjects with occupational exposure to inorganic particles (asbestos, n 1/2 19; silica, n 1/2 10; coal, n 1/2 14) were evaluated by light microscopy and transmission and scanning electron microscopy to determine the morphologic changes resulting in these cells from chronic inorganic particulate inhalation. Alveolar macrophages from dust-exposed subjects, including those who had been free of exposure to particles for more than 1 yr, contained particles of higher proportion than did those of normal unexposed subjects. Most of these particles were located within phagolysosomes. The frequency of multinucleated alveolar macrophages was significantly higher in the dust-exposed groups. Ultrastructural studies showed alterations of the morphologic aspects of the surfaces of alveolar macrophages from the dust-exposed subjects, including increased numbers of rufflings, filopodia, pinocytotic vesicles, subplasmalemmal linear densities, and increased frequency of macrophage-macrophage and macrophage-lymphocyte interactions. Furthermore, the numbers of lysosomes were significantly increased in alveolar macrophages from the dust-exposed subjects. Together, these morphologic changes are consistent with the sequelae of phagocytosis, and they emphasize both the role of alveolar macrophages in eliminating inorganic particles from the alveolar spaces and the consequences this role has in alveolar macrophage activation.

In plain English

This study examined alveolar macrophages, lung cells washed out of the lungs by bronchoalveolar lavage. It compared 43 nonsmokers or long-term ex-smokers with occupational dust exposure (19 asbestos-exposed, 10 silica-exposed, 14 coal-exposed) with 16 unexposed nonsmoking normal subjects. The asbestos-exposed subjects had worked for 32 ± 2 years as insulators, boilermakers or steamfitters in the building trades, and all had pleural changes on chest X-rays. The article does not say which asbestos fiber types these workers were exposed to. Under the light microscope, 37 ± 4% of macrophages from asbestos-exposed subjects contained particles, compared with 16 ± 1% in normal subjects. The share of particle-laden cells was not significantly different between currently exposed subjects and those free of exposure for more than 1 year. All three dust groups had more multinucleated macrophages (7 ± 1% versus 3 ± 1% in normal subjects), more ruffled cell surfaces and more lysosomes. The authors concluded that the cells showed features of "activation" consistent with a role in clearing dust. They noted that quantitative exposure histories were not available and that particles were counted only by light microscopy.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Comparative morphologic (microscopy) study of lung lavage cells from dust-exposed workers and unexposed normal subjects, using light microscopy and transmission and scanning electron microscopy
• Who was studied: 43 lifelong nonsmokers or ex-smokers who had stopped more than 5 years before the study, all with long-term occupational dust exposure: 19 asbestos-exposed (mean age 60 ± 2 years), 10 silica-exposed and 14 coal-exposed (underground West Virginia coal mines). The comparison group was 16 unexposed nonsmoking normal subjects, given as 26 ± 2 years of age in the text. Electron microscopy counts used subsets of each group.
• Exposure: Asbestos-exposed subjects had worked for 32 ± 2 years in the building trades as insulators, boilermakers or steamfitters. All had pleural changes on chest radiographs consistent with long-term asbestos exposure, and nine had not worked in the trades for more than 1 year. The article does not say which asbestos fiber types these workers were exposed to; chrysotile, crocidolite and amosite are named only in discussion of earlier studies. The other groups had silica exposure (foundry, pottery, quartz mill, diatomaceous earth) or coal mine dust exposure.
• Main results:
  • Percentage of alveolar macrophages containing particles (light microscopy): asbestos-exposed 37 ± 4%, silica-exposed 57 ± 4%, coal-exposed 74 ± 4%, normal 16 ± 1%. All comparisons to normal were p less than 0.005.
  • Percentage of macrophages containing birefringent particles: asbestos-exposed 14 ± 2%, silica-exposed 52 ± 6%, coal-exposed 65 ± 4%, normal 6 ± 1%. All comparisons to normal were p less than 0.005.
  • Within each of the three dust groups, the percentage of particle-laden macrophages was not significantly different between currently exposed subjects and those free of exposure for more than 1 year (p greater than 0.1).
  • Multinucleated macrophages: 7 ± 1% in each of the asbestos-exposed, silica-exposed and coal-exposed groups, compared with 3 ± 1% in normal unexposed subjects (p less than 0.005).
  • Macrophages with rough or ruffled surfaces: asbestos-exposed 75 ± 3%, silica-exposed 80 ± 6%, coal-exposed 72 ± 7%, normal 26 ± 6% (p less than 0.05, all compared with normal).
  • Lysosomes plus phagolysosomes per unit area (45 square micrometres): normal 56.3 ± 5.7, asbestos-exposed 98.6 ± 11.2, silica-exposed 98.0 ± 6.4, coal-exposed 118.6 ± 8.2 (each p less than 0.05 versus normal). Mitochondria were not significantly increased.
  • Attachments between macrophages, and between macrophages and lymphocytes, were commonly seen in the dust-exposed groups, particularly the asbestos-exposed group (qualitative observation).
• The authors' conclusion: The authors concluded that alveolar macrophages from subjects with occupational exposure to inorganic particles show numerous features of cellular "activation", consistent with an important role for these cells in taking up and eliminating inorganic dust particles from the alveolar spaces.
• Limitations the authors state:
  • Quantitative exposure histories were not available, so the authors could not tell whether subjects with more particle-rich macrophages had longer or more intense exposures.
  • Particles were counted only by light microscopy. The authors stated that electron microscopy would have found additional smaller particles.
  • Particle size and shape were evaluated only in two dimensions, which may not fully characterize platy or fibrous materials.
  • The authors noted that exposures were likely very heterogeneous even though each subject was assigned to a single exposure group.

Topics

Medical terms in this study, explained in our Lexicon: Alveolar Macrophage, Occupational Exposure, Bronchoalveolar Lavage (BAL), Scanning Electron Microscopy (SEM), Phagolysosome, Macrophage, Phagocytosis.

Related studies

• Sialic acid mediates the initial binding of positively charged inorganic particles to alveolar macrophage membranes — J.E. Gallagher, G. George, et al. (1987)
• Stimulation of oxidant production in alveolar macrophages by pollutant and latex particles — G.E. Hatch, D.E. Gardner, et al. (1980)
• Response of bovine alveolar macrophages in vitro to welding fume particles — L.R. White, A.B. Marthinsen, et al. (1983)
• Asbestos fibers and silica particles stimulate rat alveolar macrophages to release tumor necrosis factor. Autoregulatory role of leukotriene B4 — C.M. Dubois, E. Bissonnette, et al. (1989)
• Interleukin 1 production and accessory cell function of rat alveolar macrophages exposed to mineral dust particles — Y. Oghiso, Y. Kubota (1987)
• Inorganic particles induce secretion of a macrophage homologue of platelet-derived growth factor in a density-and time-dependent manner in vitro — R.M. Schapira, A.R. Osornio-Vargas, et al. (1991)

Browse more research in The American Review of Respiratory Disease, or return to medical research.