Dioxins and the immune system: mechanisms of interference. A meeting report.

2,3,7,8-Tetrachlorodibenzo-p-dioxin, or simply 'dioxin', is an environmental pollutant, infamous for its extremely high toxicity. Dioxin mimics the unknown natural ligand of the cytosolic arylhydrocarbon receptor which is conspicuously abundant in the thymus, and acts as a transcription factor upon ligand engagement. Thymus atrophy and immunosuppression have long been known to be major effects of dioxin exposure, evident at even very low doses. In a meeting held in Düsseldorf, FRG, the immunotoxicology of dioxin was discussed with respect to the pathomechanisms of dioxins on lymphocyte stem cells, thymus and T cells, cytokine modulation, and other components of the immune system. Such immunological insults may have consequences for the risk assessment of chemical compounds like dioxin.