Fish as biomarkers in immunotoxicology.

This paper presents an overview on the state of the art in the development and application of biomarkers for immunotoxicology in fish. There are several reasons for developing this field: many fish diseases are related to environmental quality, various environmental pollutants have immunotoxic potential and many fish diseases have an immunological component. As in immunotoxicology in general, this aspect, in fish, has received ample attention in the recent past. Much benefit has been obtained from progress in related fields of science, such as fish immunology and rodent immunotoxicology. Meanwhile there is a broad spectrum of potential biomarkers for immunotoxicology in fish, from which macrophage parameters seem to be most widely used. The application of others, such as lymphoid cell parameters is still limited, probably due to practical problems such as lack of experience with conduct, validation and interpretation. Specific problems include the paucity of background data in the case of epidemiological field studies and the important role of other (non-chemical) stress factors in the immune response, and hence the lack of specificity of potential biomarkers.