Identification of Human T Cells that Require Zinc for Growth

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Abstract
Zinc is an essential trace element required for normal function of the immune system. Deficiency of zinc results in marked thymic atrophy in experimental animals, and in man immunodeficiency is a recognized complication of zinc deprivation. Although numerous proteins require zinc as a cofactor, its precise functions in the immune system remain unknown. The mechanism by which metals stimulate lymphocytes, whether all T cells are responsive, and the relationship to zinc requirements have not been determined. We unexpectedly isolated a number of human T-cell lines that have a highly specific requirement for zinc. The ability to respond to zinc resides in only a subset of T cells since antigen-specific clones are not stimulated by zinc. Although proliferation requires the presence of antigen-presenting cells and is restricted by class II MHC antigens, antigen-presenting cells could not be pulsed with zinc to induce T-cell activation. Our results suggest that zinc-dependent T cells are a subset of CD4+ cells present in all normal individuals and that zinc stimulates their growth by novel mechanisms.