Perls' Prussian Blue Stains of Lung Tissue, Bronchoalveolar Lavage, and Sputum

Our plain-English summary of Perls' Prussian Blue Stains of Lung Tissue, Bronchoalveolar Lavage, and Sputum, by A.J. Ghio, V.L. Roggli (Journal of Environmental Pathology, Toxicology and Oncology, 2021).

The study

• Authors: A.J. Ghio, V.L. Roggli
• Journal: Journal of Environmental Pathology, Toxicology and Oncology
• Published: 2021;40(1):1-15
• Cited by: 22 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Perls' Prussian blue (PPB) stain recognizes Fe3+ associated with hemosiderin. The employment of this stain in clinical medicine and research has been extensive and novel applications continue to evolve. Ferruginous bodies are intracellular structures in lung tissue, bronchoalveolar lavage (BAL), and sputum that stain with PPB. Inhaled, insoluble, biopersistent particles and fibers are phagocytosed by lung macrophages and thought to be coated, either partially or completely, with an iron-containing protein at the interface forming a ferruginous body. These structures can be categorized as ferruginous bodies having either an inorganic or a carbonaceous core (e.g., asbestos and byssinotic bodies, respectively). In lung tissue, BAL, and sputum, the only cells that stain with PPB are macrophages. These are described as iron- and hemosiderin-laden macrophages and called either siderophages or sideromacrophages. Siderophages can be observed in the lung tissue, BAL, and sputum after various exposures and can also be associated with many different pulmonary and extrapulmonary diseases.

In plain English

This article was a narrative review, not a new study. The authors described what takes up Perls' Prussian blue, an iron stain, in lung tissue, bronchoalveolar lavage (BAL, fluid washed from the lungs) and sputum, and proposed how this staining arises. Ferruginous bodies form when lung macrophages engulf inhaled, insoluble, biopersistent particles and fibers, which are thought to become partly or completely coated with an iron-containing protein. They suggested grouping them by core, either inorganic (such as asbestos) or carbonaceous (such as cigarette smoke). Citing earlier work, they reported that asbestos bodies form mostly on fibers longer than 10 micron and on thicker fibers. They also cited reports of iron-laden cells (siderophages) in lung tissue and BAL from asbestosis patients and in Libby amphibole-exposed rodents. They argued this iron is unlikely to come from the exposure, since these structures develop after iron-free exposures such as chrysotile asbestos and wood smoke particle. The authors concluded the staining is not equivalent to iron overload able to drive oxidant generation, but often reflects iron trapped by a particle or fiber, leaving the cell functionally iron deficient.

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: Narrative review of published literature describing what stains with Perls' Prussian blue in the lung, with a proposed mechanism
• Who was studied: No study population of its own. The review drew on published reports of lung tissue, BAL and sputum from healthy and diseased people, plus some animal studies.
• Exposure: Inhaled insoluble, biopersistent particles and fibers, including asbestos, talc, kaolinite, diatomaceous earth, erionite, silica, fiberglass, refractory ceramic fibers, silicon carbide, metals, cigarette smoke, soot, wood stove particle, coal dust, cotton and synthetic fibers. Hemorrhage and various diseases were also covered.
• Main results:
  • The authors proposed classifying ferruginous bodies by an inorganic or a carbonaceous core, rather than as asbestos or non-asbestos bodies.
  • Citing earlier work, the review stated that asbestos bodies form most often on fibers longer than 10 micron and on thicker fibers.
  • According to the review, bodies with a carbonaceous core make up the majority of ferruginous bodies seen in the general population.
  • Earlier reports cited in the review found siderophages in autopsy lung tissue and in BAL from patients diagnosed with asbestosis.
  • A cited animal study found iron-laden macrophages in lung tissue from rodents exposed to Libby amphibole.
  • In BAL from healthy, unexposed people, stain-positive macrophages usually make up less than 1 to 3% of cells. After pulmonary hemorrhage, the hemosiderin-laden macrophage index reached some of the highest reported values, greater than 20%.
  • The authors argued that the iron in ferruginous bodies and siderophages is unlikely to come from the exposure, because both develop after exposures that do not have iron, such as chrysotile asbestos and wood smoke particle.
• The authors' conclusion: The authors concluded that Prussian blue staining in the lung is not equivalent to an iron overload with a capacity to catalyze oxidant generation. They concluded that it frequently indicates that an exposure such as a particle or fiber has sequestered the metal, leaving the cell functionally iron deficient.
• Limitations the authors state:
  • The authors noted that the in vitro method of producing iron-laden cells also stains other cell types, which raises the question of how relevant it is to staining in the body.

Topics

Medical terms in this study, explained in our Lexicon: Iron Stain (Prussian Blue), Bronchoalveolar Lavage (BAL), Sputum, Ferruginous Bodies, Macrophage, Ferruginous body.

Related studies

• A method for extracting ferruginous bodies from sputum and pulmonary tissue — M.J. Smith, B. Naylor (1972)
• A procedure for the isolation of amosite asbestos and ferruginous bodies from lung tissue and sputum — M.G. Williams, R.F. Dodson, et al. (1982)
• Brief inhalation of asbestos compromises superoxide production in cells from bronchoalveolar lavage — J.M. Petruska, J. Marsh, et al. (1990)
• Multinuclear giant cells in bronchoalveolar lavage in interstitial lung diseases — C. Agustí, A. Xaubet, et al. (1987)
• Assessment of hazardous dust exposure by BAL and induced sputum — E. Fireman, J. Greif, et al. (1999)
• Asbestos fibers in bronchoalveolar lavage and lung tissue of former asbestos workers — H. Teschler, K.H. Friedrichs, et al. (1994)

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