Monocyte-dependent stimulation of human T cells by zinc

Subpopulations of human peripheral blood leucocytes were isolated by nylon filtration or E-rosette separation and tested for functional activity. As shown previously, zinc ions induce DNA synthesis in unfractionated lymphocyte cultures. E-rosette-forming cells (E-RFC), obtained either by nylon wool filtration or E-rosette separation, responded well to PHA but showed only low levels of proliferative reactivity to zinc and Con A. These dminished responses could be completely restored by the addition of small numbers of autologous, mitomycin-treated monocytes; further experiments suggested that a monocyte-derived soluble factor can substitute for monocytes in this function. B lymphocyte-enriched cell populations, containing less than 1% E-RFC, did not respond to zinc and showed only marginal reactivity to PHA and Con A.