Copper induced immunomodulation in the marine mussel, Mytilus edulis

The effects on the immune response of the mussel, Mytilus edulis, of short-term, in-vivo exposure to copper were investigated under laboratory-controlled conditions. Parameters measured concentrated on the ability of the blood cells to destroy invading pathogens and included changes in the number and character of the circulating haemocytes, peroxidase and phenoloxidase enzyme activity in the blood cells, intra- and extracellular superoxide radical production, phagocytosis and uptake of neutral red. Copper concentrations of 0.02 and 0.05 ppm were found to increase significantly the total number of circulating haemocytes, while 0.2 and 0.5 ppm decreased the proportion of eosinophilic to basophilic cells. Intracellular superoxide production significantly decreased on exposure to 0.5 ppm copper, whereas phagocytic activity was stimulated at 0.2 ppm but not at 0.5 ppm. Copper exposures of 0.2 and 0.5 ppm reduced the percentage of haemocytes showing binding of lectins from Galanthus nivalis and Helix pomatia compared with haemocytes from mussels not dosed with copper. No significant alterations were found in peroxidase and phenoloxidase activity, binding of wheat germ agglutinin or uptake of neutral red. The results are discussed in the light of elucidating the possible relationship between environmental contaminants and increased disease susceptibility in aquatic organisms. The benefits of using a multi-assay approach to monitoring environmental pollution using such methods are highlighted.