Reduction of Antitumor Immunity Caused by Asbestos Exposure

Asbestos fibers are known to cause not only benign pulmonary and pleural diseases such as asbestosis and pleural plaque, but also malignant tumors such as lung cancer and malignant mesothelioma. In addition to the carcinogenic activities possessed by the fibers themselves, it has been considered that asbestos fibers may affect the human immune system. In this review, a cell culture model using a human T cell line exposed to asbestos fibers continuously and at relatively low doses to mimic exposure of environmentally and occupationally exposed people to these fibers is introduced. Although transient and high-dose exposure caused cell apoptosis, the cell line employed acquired resistance to asbestos-induced apoptosis with continuous exposure as a result of various cellular and molecular changes such as changes in cytokine production and cytoskeletal molecules. On the other hand, changes in various immune cells such as cytotoxic T lymphocytes, natural killer cells, T helper cells, and regulatory T cells by in vitro exposure using certain cell lines as well as freshly isolated peripheral blood immune cells derived from healthy volunteers revealed impairment of antitumor immunity. Thereafter, the findings obtained were confirmed using peripheral blood immune cells derived from asbestos-exposed patients with pleural plaque or mesothelioma. The findings are also shown in this chapter. Further research should explore the effects of asbestos fibers on other immune cells such as Th17, investigate the development of diagnostic markers using altered immune cells, and pursue the identification of physiological substances from plants and other sources that can halt or recover the antitumor immunity caused by asbestos exposure.