Effect of asbestos exposure on differentiation of cytotoxic t lymphocytes in mixed lymphocyte reaction of human peripheral blood mononuclear cells

Asbestos fibers are associated with tumorigenicity, and are thought to cause mesothelioma. However, their effect on immune response remains unclear. We examined the effect of asbestos exposure on differentiationof cytotoxicTlymphocytes(CTLs) inmixedlymphocyte reactions (MLR) of human peripheral blood mononuclear cells (PBMCs) upon exposure to chrysotile B (CB) or crocidolite (CR) asbestos at 5 μg/ml for 7 days. Exposure to CB duringMLR suppressed increases in the percentage and number of CD8⁺ T cells in response to allogenic cells. The cytotoxicity for allogenic targets decreased in PBMCs exposed to CB, but not CR, when compared with PBMCs without any exposure duringMLR. Exposure to CB during MLR resulted in suppression of increases in granzyme B1 cells and IFN-γ1 cells. CB exposure also resulted in suppression of increases in CD45RO⁺ effector/memory cells and CD25⁺-activated cells in CD8⁺ lymphocytes, and a decrease in CD45RA⁺ cells. CB exposure suppressed the proliferation of CD8⁺ lymphocytes without an increase in annexin V⁺ apoptotic cells in CD8⁺ lymphocytes. Moreover, the production of IL-10, IFN-γ, and TNF-α, but not IL-2, decreased in the presence of CB. These results suggest that exposure to asbestos potentially suppresses the differentiation of cytotoxic T lymphocyte, accompanied by decreases in IFN-γ and TNF-α.