Abstract
The aim of this symposium is to facilitate to know immunotoxicology, and the present lecture shows the studies about immunological effects of silica and asbestos, summarize the point of those, and finally inform that immunotoxicological knowledge is useful for understanding of the diseases. Both of exposures to silica and asbestos, composed of silica dioxide in major proportions, cause pneumoconiosis and lung cancer following inflammation. However, silicosis is associated with autoimmune diseases of rheumatoid arthritis and systemic scleroderma, whereas asbestos causes a characteristic disease of malignant mesothelioma, suggesting difference in immunological effects. Therefore, we executed fundamental experiments using cell cultures upon exposure to silica or asbestos as well as functional analyses for immune cells of patients. It was found that silica exposure caused increase in CD69+ activated T cells and decrease in Foxp3+ regulatory T (Treg) cells, while patients with silicosis showed decrease in Treg function and high soluble IL-2R as an activation marker in peripheral blood. In contrast, asbestos exposure caused decreases in activating receptors on NK cells, Th1 function of CD4+T cells and cytotoxicity of CD8+ T cells as well as increase in Treg function, while some of those alterations were also found in peripheral blood of mesothelioma patients. Those indicate that silica and asbestos not only cause chronic inflammation and lung fibrosis commonly, but also affect lymphocytic functions differently, where the former leads to over activation of immune response and the latter causes suppressed tumor immunity, linked to the related diseases. Thus, it is beneficial for understanding the disease to know immunological effects. It is expected that immunotoxicological studies will grow more, resulting in more development of toxicology.
