Effects of 0.7 PPM Ozone Exposure on Thymocytes: In Vivo and in Vitro Studies

Abstract

Inhalation of ozone has adverse effects on lung and other organs including the thy-mus, the main source of T-lymphocytes that play a central role in cellular immunity. We analyzed the effects of inhalation of ozone on different subpopulations of thymo-cytes to uncover the possible mechanisms for ozone action on the thymus. The study included in vivo and in vitro experiments on BALB/c mice exposed to 0.7ppm ozone. In the in vivo experiments, thymocytes were quantitated using monoclonal antibodies and fluorescence-activated cell sorting, and thymocyte DNA synthesis was determined. Thymus, tissue, and blood plasma were analyzed for lipid peroxidation products using the thiobarbituric acid method. In vitro experiments determined peroxidation products and the cellular toxicity of serum and components of culture media exposed to the same concentration of ozone. Results indicated that ozone exposure induced the following: (1) significant decrease in absolute thymocyte and thymocyte subpopulation numbers; (2) peroxidation products in blood plasma and thymus in vivo and in serum in vitro; and (3) exposed plasma and serum that were toxic to thymocytes in vitro and suppressed DNA synthesis. We concluded that 0.7 ppm ozone inhalation has significant adverse effects on the thymus that may lead to T-lymphocyte imbalance and alterations in peripheral lymphoid tissue. Adverse effects appear to be due to circulating lipid peroxidation products and other ozone-induced toxic substances as judged from in vivo and in vitro evaluation of exposed plasma, serum, and culture media.