Direct effects of heavy metal pollution on the immune function of a geometrid moth, Epirrita autumnata

Previously, we found that Epirrita autumnata larvae, which were fed with leaves that came from a metal polluted area, had an enhanced immune function. To investigate further the cause of the enhanced immunity we examined experimentally the direct influence of the heavy metals, copper and nickel, on the immune function of the geometrid moth we artificially added the metals to the surface of birch leaves to examine their direct effects. As a measurement of the strength of immune function, we used encapsulation rate against a nylon monofilament. A moderate amount of Ni and Cu in the diet of moth larvae increased their encapsulation rate, but a large amount of Cu caused the immune function to decrease. The results indicate that Ni and Cu have direct effects on immunity. Moderate amounts of those metals increase immune function, but large amounts lead to inhibition of immune function.