Abstract: Objective To analyze the immunotoxicity of exogenous cadmium-metallothionein(CdMT).Methods The induced CdM T was purified and used as test substance and compared with CdCl₂.The experimental animal model was established with BALB/C mice administered by gavage daily with different dosage of CdM T or CdCl₂ for 2-and 4-weeks.The proliferation and T subsets of splenic lymphocyte of treated and control groups were examined.Results Compared with the negative control and Apo MT group,the proliferation of T-lymphocyte of the CdM T and CdCl₂ groups was inhibited and the ratio of T-subsets changed.The effects of CdM T on lymphocyte function was significantly weaker than those of CdCl₂ containing the same amount of Cd²⁺.Conclusion The exogenous CdMT has lymphocyte immunotoxicity effects on the animals administered via gastro2intestine tract with a dose2and time-dependent relationship.Moreover,the effects of CdM T were obviously different from that of CdCl₂.These results provide experimental basis for explaining the biological effects of environmental cadmium exposure as well as for conducting risk assessment of cadmium.