Suppressed proliferative response of spleen T cells from metallothionein null mice

To investigate the role of metal-binding protein, metallothionein (MT), in lymphocyte activation, the mitogen-induced proliferation of freshly isolated spleen cells was compared among MT-I, II null, and control 129/Sv mice. Spleen cells from MT null mice exhibited a markedly reduced proliferation compared with control cells when stimulated by concanavalin A or anti-CD3(epsilon) mAb, but not by lipopolysaccharide, indicating that only the response of T cells to mitogens was suppressed in MT null mice. Flow cytometric analysis of unstimulated spleen cells demonstrated no significant difference in the relative percentages of either B220+ and CD3+ cells or CD4+ and CD8+ cells between the two strains of mice. The production of interleukin (IL)-2 by MT null spleen cells after the stimulation by anti-CD3(epsilon) mAb was lower than that of control spleen cells, especially within 24 hr after the stimulation. The addition of IL-2 recovered the proliferation of MT null spleen cells to the control level. The reduced proliferative response to mitogenic stimulation of MT null T cells was confirmed by using purified splenic T cells. These results suggest that the MT expressed at basal level in the splenocytes plays an important role in T cell mitogen-induced proliferative response, probably by positively regulating the production of IL-2.