The mechanism of formation of asbestos bodies

Our plain-English summary of The mechanism of formation of asbestos bodies, by S.K. Botham, P.F. Holt (The Journal of Pathology and Bacteriology, 1968).

The study

• Authors: S.K. Botham, P.F. Holt
• Journal: The Journal of Pathology and Bacteriology
• Published: 1968;96(2):443-53
• Cited by: 36 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Fibres of inhaled anthophyllite asbestos were found in the respiratory bronchioles of guinea-pigs 3 hr after the commencement of the inhalation period. After a further 3 hr, during which time the guinea-pigs inhaled no more asbestos dust, fibres were also found in the alveoli. The first pathological effect observed was haemorrhage from alveolar capillaries, which is followed by haemolysis of extravascular red cells and the formation of granules, which are iron-containing degradation products of haemoglobin (haemosiderin). These granules are found in macrophages together with a solubilised iron-containing product (? ferritin) diffusing throughout the cytoplasm. If the macrophage has also ingested asbestos fibres, the ferritin is then often adsorbed on to the asbestos. Almost invariably only one fibre becomes coated, this being usually the longest. Other fibres in the same macrophage remained uncoated for the duration of the experiment. The ferritin coating increases in thickness and, after about 4 wk, changes in the shape of the coating appeared. The cell meanwhile shrinks on to this structure, sometimes with rupture of the cell wall, and substances from the cytoplasm are adsorbed. The coating is first smooth, then corrugated and then it takes up a beaded form. After about 10 wk the structure becomes finely beaded and may begin to fragment.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.

In plain English

This was an animal experiment in which the authors traced, step by step, how asbestos bodies (asbestos fibres coated with an iron-containing protein) form in the lung. Guinea-pigs breathed anthophyllite asbestos dust for 3, 6, 24, 25 or 50 hours. They were killed between 3 hours and 270 days after dusting began, and undusted control animals were also examined. Fibres reached the airways within 3 hours and at first showed no coating. The earliest effect the authors saw was bleeding (haemorrhage) in the lung. Giant cells began to form between 25 hours and 3 days. Iron-staining coatings on fibres inside scavenger cells (macrophages) became obvious at 4 to 7 days and increased in the second week. Young asbestos bodies appeared at 26 to 27 days. Between 91 and 270 days the lungs showed severe consolidation and many well-formed, often beaded asbestos bodies, with isolated fragmentation. When a cell held several fibres, usually only the longest was coated. The authors concluded that forming an asbestos body requires both a fibre and haemoglobin breakdown products in the same cell.

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: Animal experiment (inhalation study in guinea-pigs with microscopic examination of lung sections at timed intervals)
• Who was studied: Guinea-pigs, numbered 1 to 26 in the article's table, killed at intervals from 3 hours to 270 days after dusting began, plus control animals that received no dust (number of controls not stated); work done at the Department of Chemistry, University of Reading
• Exposure: Inhaled anthophyllite asbestos dust, given continuously in a dust tunnel for 50, 25, 24, 6 or 3 hours
• Main results:
  • In animals killed 3 and 6 hours after dusting began, no fibre showed any coating, even inside macrophages
  • Haemorrhage was one of the earliest effects of the dust
  • The number of haemorrhagic sites fell after 3 days in animals that inhaled dust for 25 hours, but not until 6 days in animals given double the dust load
  • All animals killed 25 hours to 3 days after dusting began showed the beginning of giant-cell formation
  • In animals killed 4 to 7 days after dusting began, many fibres inside macrophages or giant cells stained with the iron stain (Perls' reagent)
  • In animals killed 8 to 16 days after dusting began, iron-staining material on fibres inside cells increased and gave the fibres an irregular outline
  • In animals killed 26 to 27 days after dusting began, some of the longest fibres showed the colour of typical asbestos bodies
  • Animals killed 91 to 270 days after dusting began showed severe lung consolidation and numerous well-formed asbestos bodies of different types
  • Isolated fragmentation of finely beaded asbestos bodies occurred in the older animals of the 91 to 270 day group
  • When a macrophage contained more than one fibre, it was almost always the longest fibre that was coated
• The authors' conclusion: The authors concluded that an asbestos body forms only when an asbestos fibre and haemoglobin breakdown products are in the same cell. In their account, an iron-containing product (which they tentatively identified as ferritin) is adsorbed onto fibres inside macrophages. The coating then thickens, becomes corrugated and beaded, and may later fragment.
• Limitations the authors state:
  • The brief dust exposures used meant that few asbestos bodies developed
  • The authors could not tell with certainty whether the haemorrhage was caused by mechanical or chemical damage
  • It was uncertain whether macrophages took up haemoglobin itself or its breakdown product

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Asbestos Bodies, Anthophyllite, Alveoli, Macrophage, Ferritin.

Related studies

• Development of asbestos bodies on amosite, chrysotile and crocidolite fibres in guinea-pig lungs — S.K. Botham, P.F. Holt (1971)
• The development of glass-fibre bodies in the lungs of guinea-pigs — S.K. Botham, P.F. Holt (1971)
• Asbestos-body formation in the lungs of rats and guinea-pigs after inhalation of anthophyllite — S.K. Botham, P.F. Holt (1972)
• Formation of asbestos bodies under the influence of parenteral iron overload — S. Narang, J.L. Kaw, et al. (1978)
• Further observations on the ultrastructure and chemistry of the formation of asbestos bodies — J.M. Davis (1970)
• Comparison of effects of glass fibre and glass powder on guinea-pig lungs — S.K. Botham, P.F. Holt (1973)

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