Effects of methyl mercury exposure on spleen and blood natural killer (NK) cell activity in the mouse.

The effect of 12 weeks of exposure to methyl mercury (MeHg) (3.9 micrograms/g diet) on the immune function was studied in female Balb/c mice. This MeHg dose did not affect body, kidney, liver or spleen weight. Thymus weight and cell number decreased by 22% (P less than 0.05) and 50% (P less than 0.001), respectively. The lymphoproliferative response to T and B cell mitogens, however, tended to increase in both lymphoid organs. Natural killer cell activity was reduced by 44% (P less than 0.01) and 75% (P less than 0.05) in the spleen and blood, respectively. The number of red blood cells increased slightly (12%, P less than 0.05), whereas white blood cell counts were unaffected. These results indicate that MeHg evokes immune suppressive effects on protective cytotoxic capacity that is of major importance in the pathogenesis of several diseases.