Zinc homeostasis and immunosenescence.

For more than 50 years, zinc is known to be an essential trace element, having a regulatory role in the immune system. Deficiency in zinc thus compromises proper immune function, like it is observed in the elderly population. Here mild zinc deficiency is a common condition, documented by a decline of serum or plasma zinc levels with age. This leads to a dysregulation mainly in the adaptive immunity that can result in an increased production of pro-inflammatory cytokines, known as a status called inflamm-aging. T cell activation as well as polarization of T helper (Th) cells into their different subpopulations (Th1, Th2, Th17, regulatory T cells (Treg)) is highly influenced by zinc homeostasis. In the elderly a shift of the Th cell balance towards Th2 response is observed, a non-specific pre-activation of T cells is displayed, as well as a decreased response to vaccination is seen. Moreover, an impaired function of innate immune cells indicate a predominance of zinc deficiency in the elderly that may contribute to immunosenescence. This review summarizes current findings about zinc deficiency and supplementation in elderly individuals.