Decrease in Intracellular Perforin Levels and IFN-γ Production in Human CD8+ T Cell Line following Long-Term Exposure to Asbestos Fibers

Our plain-English summary of Decrease in Intracellular Perforin Levels and IFN-γ Production in Human CD8+ T Cell Line following Long-Term Exposure to Asbestos Fibers, by N. Kumagai-Takei, Y. Nishimura, H. Matsuzaki, et al (Journal of Immunology Research, 2018).

The study

• Authors: N. Kumagai-Takei, Y. Nishimura, H. Matsuzaki, S. Lee, K. Yoshitome, T. Otsuki
• Journal: Journal of Immunology Research
• Published: 2018;2018:4391731
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Although the tumorigenicity of asbestos, which is thought to cause mesothelioma, has been clarified, its effect on antitumor immunity requires further investigation. We previously reported a decrease in the percentage of perforin+ cells of stimulated CD8+ lymphocytes derived from patients with malignant mesothelioma. Therefore, we examined the effects of long-term exposure to asbestos on CD8+ T cell functions by comparing long-term cultures of the human CD8+ T cell line EBT-8 with and without exposure to chrysotile (CH) asbestos as an in vitro model. Exposure to CH asbestos at 5 μg/ml or 30 μg/ml did not result in a decrease in intracellular granzyme B in EBT-8 cells. In contrast, the percentage of perforin+ cells decreased at both doses of CH exposure. CH exposure at 30 μg/ml did not suppress degranulation following stimulation with antibodies to CD3. Secreted production of IFN-γ stimulated via CD3 decreased by CH exposure at 30 μg/ml, although the percentage of IFN-γ + cells induced by PMA/ionomycin did not decrease. These results indicate that long-term exposure to asbestos can potentially suppress perforin levels and the production of IFN-γ in human CD8+ T cells.

In plain English

This laboratory study used EBT-8, a human CD8+ T cell line (immune cells that can kill tumor cells) originally established from a patient with large granular lymphocyte leukemia. The authors grew the cells for more than 1 month but less than 2 months with chrysotile asbestos at 0, 5 or 30 μg/ml. In separate 48-hour tests, growth was inhibited at chrysotile doses over 50 μg/ml. In the long-term cultures, levels of granzyme B, a cell-killing protein, did not differ significantly between exposed and unexposed cells. The percentage of cells containing perforin, another cell-killing protein, was significantly lower at both 5 and 30 μg/ml. Release of the cells' killing granules did not differ significantly at 30 μg/ml. After stimulation through the CD3 receptor, cells exposed to 30 μg/ml secreted significantly less IFN-γ, an immune signaling protein. After a different stimulation, the percentage of IFN-γ-positive cells did not decrease at 5 μg/ml. The authors concluded that long-term asbestos exposure in vitro has the potential to suppress certain CD8+ T cell functions, and suggested testing another cell line.

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 comparing long-term cultures of a human cell line with and without chrysotile asbestos; no people or animals were exposed
• Who was studied: The human CD8+ T cell line EBT-8, originally established from cells of a patient with large granular lymphocyte leukemia of T cell origin; provided to the authors by Prof. H. Asada; work done at Kawasaki Medical School, Japan
• Exposure: Chrysotile asbestos (UICC standard samples of chrysotile A and B, and the JASFM standard chrysotile sample JAWE 131) at 0, 5 or 30 μg/ml, continuously for more than 1 month but less than 2 months. Short 48-hour growth tests used 0 to 100 μg/ml.
• Main results:
  • Short-term (48-hour) exposure: growth of EBT-8 cells was inhibited by UICC chrysotile at over 50 μg/ml. The same was seen with JASFM chrysotile.
  • Cells exposed long-term to 5 μg/ml chrysotile (EBT-8-CH5) compared with unexposed cells (EBT-8-Org), 14 independent experiments: granzyme B levels showed no significant difference. The percentage of perforin-positive cells was significantly decreased (p less than 0.01).
  • Cells exposed long-term to 30 μg/ml chrysotile (EBT-8-CH30) compared with unexposed cells, 14 independent experiments: granzyme B showed no significant difference. The percentage of perforin-positive cells was significantly decreased (p less than 0.01).
  • Degranulation (measured as cell-surface CD107a after anti-CD3 stimulation) increased in both unexposed and 30 μg/ml-exposed cells, with no significant difference between them (4 independent experiments).
  • After PMA/ionomycin stimulation, the percentage of IFN-γ-positive cells was not decreased in 5 μg/ml-exposed cells compared with unexposed cells (11 independent experiments).
  • After 48 hours of stimulation with anti-CD3 beads, IFN-γ secreted into culture fluid was significantly lower in 30 μg/ml-exposed cells than in unexposed cells (p less than 0.0001; 20 independent experiments).
• The authors' conclusion: The authors concluded that long-term in vitro exposure to asbestos has the potential to suppress certain functions of CD8+ T cells. They called for further study of the mechanisms involved.
• Limitations the authors state:
  • The findings come from in vitro (laboratory) experiments.
  • Only one cell line was used; the authors suggested another cell line could help confirm the results.
  • Only granzyme B was examined; other granzymes might be altered by chronic chrysotile exposure.
  • How chronic chrysotile exposure affected the cells' functions remains unclear.
  • The differing IFN-γ results might reflect the different doses used (5 versus 30 μg/ml) rather than the different stimulation methods.
  • Perforin and granzyme B levels in EBT-8 cells vary with handling conditions such as freezing and storage. The granzyme B level of the unexposed control cells differed between experiments.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile, Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Mesothelioma, Malignant Mesothelioma, Chrysotile.

Related studies

• Functional properties of CD8(+) lymphocytes in patients with pleural plaque and malignant mesothelioma — N. Kumagai-Takei, Y. Nishimura, et al. (2014)
• Decrease in phosphorylation of ERK following decreased expression of NK cell-activating receptors in human NK cell line exposed to asbestos — Y. Nishimura, M. Maeda, et al. (2009)
• The Effects of Asbestos Fibers on Human T Cells — N. Kumagai-Takei, S. Lee, et al. (2020)
• Enhancement of regulatory T cell-like suppressive function in MT-2 by long-term and low-dose exposure to asbestos — C. Ying, M. Maeda, et al. (2015)
• Aberrant expression of FoxP3 in a human T cell line possessing regulatory T cell‑like function and exposed continuously to asbestos fibers — M. Maeda, H. Matsuzaki, et al. (2018)
• IL4I1: an inhibitor of the CD8⁺ antitumor T-cell response in vivo — F. Lasoudris, C. Cousin, et al. (2011)

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