Activation of human CD4⁺CD45RA⁺ T cells by chrysotile asbestos in vitro

Chrysotile asbestos stimulates T lymphocyte subsets. Cell surface CD4 or CD45RA expression in peripheral blood mononuclear cells (PBMC) was downregulated after incubation with chrysotile asbestos in vitro temporatily. The percentage of CD4⁺CD45RA⁺ cells and mean fluorescence intensity in CD4 or CD45RA decreased after incubation with asbestos and returned to the original level after 24 h of incubation, which suggests that chrysotile asbestos activates CD4⁺CD45RA⁺ cells. No change was observed in CD29 expression. An increased percentage of lL-2R positive cells and an elevated intracellular Ca⁺⁺ level were also indicative of the activation of PBMC by chrysotile asbestos.