of serum levels for selective suppression of leukocyte subsets 1 is too small to adjust by oral administration.
In the study by Reinhold et al. 11 the longterm treatment of patients with zinc resulted in decreased serum levels of interleukin 6 (IL-6) and IL-10. However, this is not a result of monocyte toxicity as the serum zinc level only increases up to a mean value of 14 M. This decreasing effect might be driven by induction of heat shock proteins 12 , but it seems more likely to be an effect of cytokine half-life, regulated by โฃ 2 -macroglobulin 13 . Zinc transforms โฃ 2 -macroglobulin into its active fast form, which interacts with various cytokines influencing the half-life in serum, its biological activity or its detection by antibodies 13 .
Taken together, zinc influences various immune functions, as well as leukocyte biology and general cell functions. Furthermore, many proteins have zinc-binding motifs that alter their function. In conclusion, the effect of zinc treatment must be discussed in detail, as the alteration of immunological parameters is sometimes driven by the nonimmunological effects of zinc 14 . Finally, immunosuppression by zinc might be useful in some cases but, to date, has not been discussed adequately in the literature .