Differential susceptibility of T- and B-lymphocyte proliferation to cadmium: relevance to zinc requirement in T-lymphocyte proliferation.

Effect of zinc on an inhibitory action of cadmium to mitogen-induced lymphocyte proliferation was investigated. Cadmium at concentrations below 10 microM selectively inhibited concanavalin A-induced T-cell proliferation as compared with bacterial lipopolysaccharide-induced B-cell proliferation. Such differential susceptibility of T- and B-cell proliferation was not observed in the cases of other cations such as mercury, lead, nickel, molybdenum, chromium(VI) and arsenic (V). The inhibitory effect of 10 microM cadmium on T-cell proliferation was almost completely prevented by addition of 30 microM zinc to the culture medium, but was not by ferrous iron, nickel and copper. Further, cadmium exerted the same extent of inhibition even when it was added at 16 h after concanavalin A stimulation, and thereafter the inhibition gradually decreased. Correlated well with this observation, the protective effect of zinc was seen as far as it existed during the first 16 h of the mitogen stimulation. As intracellular cadmium content and a cadmium-induced metallothionein level were not changed by zinc addition, these observations strongly suggest that cadmium inhibits some zinc-dependent processes required for T-cell proliferation.