Effect of zinc administration on cadmium-induced suppression of natural killer cell activity in mice

Natural killer (NK) cells play an important role in immune surveillance against viral infections and neoplasms. The effect of cadmium with or without zinc on mouse spleen NK cell activity was studied. Six-week-old male C57BL/6 mice were given drinking water containing either 50 ppm cadmium, 50 ppm cadmium together with 500 ppm zinc, or 500 ppm zinc. A fourth group receiving no additional cadmium or zinc served as control. After 3 weeks of treatment, the mice were killed, splenic lymphocytes isolated and cultured with 51Cr-labelled YAC-1 target cells for 4 and 12 h in a ratio of 50:1. The percentage of target cell lysis was measured to assess NK cell activity. In the 12-h assay, cadmium-treated animals had significantly lower NK cell activity than controls. Concurrent zinc administration prevented the suppression. In the 4-h assay, a similar trend was observed. Between 4 and 12 h, NK cell activity increased significantly in control and zinc-treated groups, but not in those receiving cadmium. The results suggest that a relatively low dose of cadmium suppresses NK cell activity, which can be prevented by a moderately large dose of zinc.