[Influence of mercury on thymulin production: metallothioneins role]

Occupational or environmental exposure to various metals affects human health. In particular, mercury is known to affect the immune system adversely. Metallothioneins (MTs) are low molecular weight, cysteine-rich, intracellular proteins, with high affinity for bivalent metals of which they regulate intracellular concentrations, thereby being playing a fundamental role in metal homeostasis. MTs protect cells from stress, inflammation and free radical damage and are involved in zinc homeostasis. Zinc has an important role in the immune system because it is indispensable for the activation andfunctioning of the thymic hormone, thymulin, which in turn is involved in T-lymphocyte differentiation and maturation. MTs participate in the detoxification process following acute poisoning, and are expressed in the various tissues, as well as in chronic intoxication, where continuous stress and the persistent inflammatory state induce their over-expression. The present study was undertaken to gain insights into the potential mechanisms acting on the immune system/altering the immune status in the presence of low mercury concentrations. To do this, the genic expression of MT-I and the amount of active thymulin produced by thymic endothelial cells were studied in mice exposed to different doses of mercury.