Monitoring the effects on the human immune system by xenobiotics. The example of styrene.

Adverse effects of xenobiotics on the immune system may be associated with a broad spectrum of possible short-term and long-term end-points, including hypersensitivity, autoimmunity, increased susceptibility to infectious agents and even an increased risk for cancer. To mintor the immune system, great efforts have been made in searching for accessible and reliable indicators, including responses to mitogens, plaque-forming cells, detection of specific cellular products, mixed lymphocyte reaction, lymphocyte cytotoxicity evaluation. However, the quantitative assessment of immune funtions id difficult because of the nature of the immune response and our limited acess to the active elements of this system of defence. Although peripheral lymphocytes represent less than 0,5% of the total lymphocyte mass, their phenotypic analysis based on monoclonal antibodies and automated flow cytometry has been proposed as a promising approach to immunotoxicology. In this paper, we report the results of phenotypic analysis in peripheral lymphocytes from workers exposed to styrene. As a whole, these studies suggest that, in spite of a decrease in the CD4+ subset, occupational exposure to styrene is associated with an apparent activation of lymphocyte subsets involved in specific cellular immunity. However, whether phenotype analysis actually mirrors functional changes still remains to be verified. Work is in progress to asses whether changes in natural cytotoxicity of lymphocytes is associated with the dose-dependent increase in NK subset found among styrene exposed workers.