Suppressed Immune System Caused by Exposure to Asbestos and Malignant Mesothelioma

Abstract

Mesothelioma is the most serious of the asbestos-related diseases. It is caused by exposure to relatively low doses of asbestos and takes a long period to develop, which suggests the enactment of gradual adverse effects other than cellular toxicity. The immune system, which can play a role in tumor prevention, is a presumable target of asbestos by accumulation in lymph nodes and then slowly affecting functions of immune cells. Here, we describe key findings obtained from our studies concerning the immune-suppressive effects of asbestos and functional alteration in immune cells of patients with mesothelioma as well as plaque-positive subjects. Asbestos exposure of cell cultures resulted in decreased natural and acquired cytotoxicity exerted by NK cells and CTLs and the ability of Th1 cells to activate and support antitumor immunity. In contrast, asbestos exposure augmented Treg cell function and generation of fibrogenic/suppressive macrophages. Mesothelioma patients also showed similar characteristics in certain alterations caused by asbestos exposure. Additionally, our recent study established immunological screening devices for mesothelioma and asbestos exposure on the basis of comprehensive analysis of peripheral blood. Those findings underscore the importance of the immunological effects of asbestos and should assist further understanding of the mechanism and early detection of mesothelioma.