Surface morphology and correlated phagocytic capacity of pulmonary macrophages lavaged from the lungs of rats

Our plain-English summary of Surface morphology and correlated phagocytic capacity of pulmonary macrophages lavaged from the lungs of rats, by D.B. Warheit, L.H. Hill, A.R. Brody (Experimental Lung Research, 1984).

The study

• Authors: D.B. Warheit, L.H. Hill, A.R. Brody
• Journal: Experimental Lung Research
• Published: 1984;6(1):71-82
• Cited by: 53 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The morphology and phagocytic capacities of pulmonary macrophages recovered by lavage from normal rats were studied in vitro after incubation under various culture conditions. Most adherent macrophages (73 +/- 6%) were flat and exhibited ruffled surfaces. Phagocytosis of carbonyl iron beads by pulmonary macrophages was quantitated using secondary and backscattered electron microscopic techniques. Our results show that macrophage surface features correlate with the phagocytic capacity of the cells, that is, macrophages with ruffled membranes phagocytose a significantly greater number of iron beads than do smooth, unruffled cells (P less than or equal to 0.001). Moreover, an enhanced percentage of smooth cells (48%) was found in populations of tracheobronchial macrophages; this finding correlated with a reduced phagocytic potential. When the percentages of smooth cells were increased experimentally by incubating cells with silica or varying pH conditions, the number of macrophages devoid of carbonyl iron beads was enhanced. The results show that smooth macrophages are functionally impaired compared with ruffled cells. These studies form the basis for assessing functional alterations of macrophages exposed in vivo to inhaled toxic particulates such as chrysotile asbestos and silica.

In plain English

In this laboratory study, the authors washed immune cells called macrophages from the lungs of healthy male rats and examined them under an electron microscope. They sorted cells as ruffled or smooth and counted the carbonyl iron beads each had swallowed. In untreated populations, 73 plus or minus 6% of cells attached to the dish were flat and ruffled. After one hour, about 25% of ruffled cells but about 89% of smooth cells had swallowed no beads (p less than 0.001). Macrophages washed only from the airways included more smooth cells (48%). These were less often alive (77.8% versus 92.9% for whole-lung cells), and more of them took up no beads. Silica raised the share of smooth and bead-free cells. At pH 2 most cells died; at pH 5 and 9 viability was unchanged, but ruffled cells and bead uptake fell versus pH 7. The authors concluded that surface appearance is related to a macrophage's ability to swallow particles. They called this relevant to studying macrophages exposed in living animals to inhaled chrysotile asbestos and silica. Asbestos itself was not tested here.

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: Laboratory (in vitro) experiment on rat lung macrophages recovered by lavage and studied by scanning electron microscopy
• Who was studied: Male CD (SD) BR rats aged 8-10 weeks. Macrophages were recovered by whole-lung lavage and by a separate tracheobronchial (airway-only) lavage. Table 3 lists 14 animals for tracheobronchial lavage and 9 for whole-lung lavage.
• Exposure: Cultured macrophages were given serum-coated carbonyl iron beads (0.4 to 3 micrometers) to measure uptake. In separate experiments they were exposed to silica (Min-U-Sil) at 100, 500 and 1000 per ml, or to culture fluid at pH 2, 5, 7 or 9 for 1 hour. The silica unit is printed as 'kg/ml' in the scan; the figure label suggests micrograms. No asbestos was used.
• Main results:
  • In untreated macrophage populations, 73 plus or minus 6% of the cells that attached to the culture dish spread out with ruffled surfaces; the remaining macrophages were smooth.
  • After 1 hour, about 25% of ruffled macrophages had taken up no iron beads, versus 89% of smooth macrophages. Table 2 gives these as 25.8 plus or minus 8.3% versus 88.8 plus or minus 9.3%, p less than 0.001.
  • Macrophages from tracheobronchial lavage had an increased share of smooth cells (48%), which the authors linked to reduced phagocytic potential. In Fig. 4 this was measured as an increased percentage of cells that failed to take up any iron beads.
  • Viability of tracheobronchial macrophages was 77.8 plus or minus 11.2% (14 animals), versus 92.9 plus or minus 4.4% for whole-lung macrophages (9 animals). The difference was reported as statistically significant (p less than 0.05).
  • The lowest silica dose did not change viability after 1 hour (93 plus or minus 5% versus 95 plus or minus 3% in controls). Silica-exposed populations (n = 3 rats) showed more smooth cells, and uptake fell as the silica dose increased.
  • At pH 2 most cells became necrotic, and virtually all lacked ruffles and internalized beads. At pH 5 and 9, viability was unchanged (92 plus or minus 4%), but there were fewer ruffled cells and less bead uptake than at pH 7.
• The authors' conclusion: The authors concluded that macrophage surface morphology is related to phagocytic capacity and that smooth macrophages are functionally impaired. They stated this is relevant for assessing macrophages exposed in living animals to inhaled particles such as chrysotile asbestos and silica.
• Limitations the authors state:
  • The authors state that further kinetic studies would be needed to determine the age and origin of the tracheobronchial macrophages.
  • About 5-10% of cells were 'intermediate', with few ruffles. Because their significance was hard to assess, they were grouped with ruffled cells.

Topics

Medical terms in this study, explained in our Lexicon: Macrophage, Phagocytosis, Chrysotile.

Related studies

• Production of arachidonic acid metabolites by macrophages exposed in vitro to asbestos, carbonyl iron particles, or calcium ionophore — S. Kouzan, A.R. Brody, et al. (1985)
• Macrophage phagocytic activity and cell phagocytic capacity following intratracheal instillation of a comixture of asbestos fibers — I. Trosic, M. Matausic-Pisl, et al. (1995)
• Phagocytosis of asbestos fibers by human pulmonary alveolar macrophages — T. McLemore, M. Corson, et al. (1979)
• 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)
• One-year follow-up of the phagocytic activity of leukocytes after exposure of rats to asbestos and basalt fibers — M. Hurbánková (1994)
• Sialic acid mediates the initial binding of positively charged inorganic particles to alveolar macrophage membranes — J.E. Gallagher, G. George, et al. (1987)

Browse more research in Experimental Lung Research, or return to medical research.