Xenobiotic-induced immunomodulation in the European flat oyster, Ostrea edulis.

The presence of chemical contaminants in marine coastal waters is a major subject of concern since many molecules are potentially immunotoxic, even at low concentration. During the last decade, studies in sentinel species, such as the blue mussel, Mytilus edulis, or the Pacific oyster, Crassostrea gigas, have revealed that immunosuppressive responses can be related to xenobiotic exposure, in the laboratory and in the field. In the present study, European flat oysters were experimentally exposed to heavy metals, to investigate possible alterations of their immune function. Several hematological and functional parameters of hemocytes were measured by flow cytometry, a technique allowing rapid, sensitive, cell-by-cell measurements in large cell populations. Results reveal a depression of phagocytosis and several subcellular, physiological changes in oysters exposed to cadmium alone or to cadmium and copper, suggesting an overall alteration of the phagocytic function.