Analysis of depressed cell-mediated immunity in asbestos workers

Our plain-English summary of Analysis of depressed cell-mediated immunity in asbestos workers, by R.D. deShazo, J. Nordberg, Y. Baser, et al (The Journal of Allergy and Clinical Immunology, 1983).

The study

• Authors: R.D. deShazo, J. Nordberg, Y. Baser, B. Bozelka, H. Weill, J. Salvaggio
• Journal: The Journal of Allergy and Clinical Immunology
• Published: 1983;71(4):418-24
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

To explore the mechanisms of asbestos-related perturbations of the immune system, we evaluated the in vitro cell-mediated immunity of five asymptomatic asbestos workers with hypergammaglobulinemia and decreased T-cell numbers. These results were compared with those in 10 matched controls. Analysis of T-lymphocyte populations revealed decreased absolute numbers of OKT4+ (helper/inducer) T cells in the peripheral blood and phytohemagglutinin (PHA)-stimulated mononuclear cell cultures of the workers. When chrysotile asbestos was added to PHA cultures, expansion of OKT4+ cell populations was disproportionately inhibited in workers' cultures. Furthermore, control proliferative responses to PHA became indistinguishable from initial worker responses. These effects were incompletely explained by the cytotoxic effects of asbestos on cultured lymphocytes. We conclude that both in vivo and in vitro exposure of mononuclear cell populations to asbestos may lead to a diminution of helper-inducer T-cell numbers. In asbestos-exposed individuals, this latter lymphocyte subpopulation appears to be especially sensitive to in vitro asbestos exposure. Although the clinical implications of these findings are unclear, we hypothesize that many of the immunologic abnormalities that occur in asbestos workers could be explained by direct asbestos effects on the OKT4+ immunoregulatory population.

In plain English

This was a laboratory study of blood cells from five asymptomatic asbestos cement workers exposed to chrysotile asbestos. They were randomly chosen from 40 long-term exposed workers found to have high blood antibody levels. Their cells were compared with those of 10 healthy municipal workers of similar age and smoking habits who had no occupational asbestos exposure. The workers had fewer helper/inducer (OKT4+) T cells in their blood than the controls (508 vs 802 cells/mm3). Their cells also multiplied less when stimulated with a substance called PHA (phytohemagglutinin). When chrysotile fibers were added to the cell cultures, responses fell in both groups. Control cells with asbestos became indistinguishable from worker cells without fibers. Worker cells were inhibited more: at one PHA dose, responses dropped 44.2% in workers versus 24.7% in controls. Asbestos held back the growth of OKT4+ cells in both groups, more so in workers. The authors said cell death caused by the fibers was too small to fully explain these effects. They concluded that workers' helper/inducer cells seemed selectively inhibited by asbestos in the laboratory, but that this had not been conclusively shown to be the sole mechanism.

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) study of blood immune cells from asbestos workers compared with matched controls, before and after stimulation with PHA and with chrysotile fibers added to the cultures
• Who was studied: Five asymptomatic asbestos cement workers, randomly selected from 40 workers with long-term asbestos exposure and hypergammaglobulinemia (high blood antibody levels), part of an ongoing study (Tulane University, New Orleans). They had a mean of 240 months of exposure. On ILO X-ray grading, two were 0/0, two 0/1 and one 1/1. Controls were 10 healthy age- and smoking-matched municipal workers with no history of occupational asbestos exposure.
• Exposure: Occupational exposure to chrysotile asbestos in asbestos cement work. In the laboratory, International Union Against Cancer chrysotile fibers were added to cell cultures at 125 micrograms per milliliter.
• Main results:
  • Workers' blood lymphocytes multiplied significantly less than controls' in response to PHA across the dose range.
  • Workers had fewer total T cells (OKT3+) in blood than controls: 792 vs 1206 cells/mm3.
  • Workers had significantly fewer helper/inducer (OKT4+) T cells in blood than controls: 508 vs 802 cells/mm3.
  • Suppressor/cytotoxic (OKT8+) cell numbers (210 in workers vs 245 in controls) and OKT4/OKT8 ratios were not significantly different between the groups.
  • When chrysotile was added, control cell responses became indistinguishable from those of worker cultures without fibers.
  • Asbestos inhibited workers' cell responses significantly more than controls' at most PHA doses. At 5 micrograms per milliliter of PHA, the mean drop was 24.7% for controls and 44.2% for workers.
  • In PHA-stimulated cultures, absolute numbers of OKT4+ cells were significantly lower in worker cultures on days 4 and 6.
  • Adding asbestos inhibited the expansion of OKT4+ cells, and so of total T cells, in both groups, to a significantly greater degree in workers' cultures.
  • Asbestos caused greater cell death among worker lymphocytes than control lymphocytes, but the authors judged the cell-killing effect too small to fully explain the decreases.
• The authors' conclusion: The authors concluded that the helper/inducer lymphocyte population of asbestos workers seemed to be selectively inhibited by asbestos in vitro.
• Limitations the authors state:
  • The authors stated that effects on the OKT4+ cell population had not been conclusively shown to be the sole mechanism behind the reduced cell multiplication.
  • The authors stated that any role of macrophages in the observed T-cell changes was unclear and needed further investigation.
  • The authors stated that the findings did not explain the heightened antibody responses seen in asbestos workers.

Topics

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

Medical terms in this study, explained in our Lexicon: Chrysotile, Asbestos Exposure.

Related studies

• Identification of environmental carcinogens utilizing T-cell mediated immunity — R.H. Stevens, D.A. Cole, et al. (1986)
• Immunological studies of patients with asbestosis. I. Studies of cell-mediated immunity — E. Kagan, A. Solomon, et al. (1977)
• Identification of carcinogens by measurement of cell-mediated immunity. III. Immunity to asbestos-induced rat peritoneal mesothelioma — D.A. Cole, R.H. Stevens, et al. (1982)
• Assessment of cell-mediated immunity to malignant mesothelioma by microcytotoxicity tests — M.J. Embleton, J.C. Wagner, et al. (1976)
• Manifestations of cellular immunity in the rat after prolonged asbestos inhalation. II. Alveolar macrophage-induced splenic lymphocyte proliferation — K. Miller, E. Kagan (1981)
• Immunologic aberrations in asbestos cement workers: dissociation from asbestosis — R.D. deShazo, D.J. Hendrick, et al. (1983)

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