Studies on immunomodulation in fish with emphasis on polycyclic aromatic hydrocarbons in dab Limanda limanda, L.
The aims of the work reported in this thesis were threefold; firstly, to investigate the effect of experimental exposure to polycyclic aromatic hydrocarbons (PAHs) on the immune response of dab (Limanda limanda), a sentinel species of flat fish for pollution studies, and rainbow trout (Oncorhynhus mykiss); secondly, to then go into the field to investigate the effects of exposure to PAHs on dab immunity through a major oil spill and thirdly, to increase current knowledge on the cellular immune functions of dab so as to provide better assays for biomonitoring purposes. Chapter 1 of this thesis is a general introduction to immunotoxicology, subspeciality of toxicology, which described brief accounts for both immunology and toxicology. Some brief accounts for the use of fish (lower vertebrates) in a pollution monitoring programme and the toxicology aspects of polycyclic aromatic hydrocarbons, were also given. In chapter 2, a laboratory exposure of animals to oil-contaminated sediment was established where four doses of diesel oil-based drilling mud used, i.e. 4, 8 (seen 500m from oil exploration platforms in the North Sea), 12 and 16% (w/w), with two exposure times employed, i.e. 2 and 4 weeks. Haematocrits and lymphocyte numbers tend to increase with low diesel oil doses, whereas high doses (particularly with longer exposure) gave significantly decreased values. Serum lysozyme levels were decreased, but serum bactericidal and anti-protease activities tended to increase following exposure. Kidney phagocyte respiratory burst and neutrophil migration activity also showed a trend to lower levels relative to control fish, whereas the number of antibody-secreting cells were increased with high drilling mud concentration. Lastly, there was a dose-dependent hepatomegaly. In chapter 3, rainbow trout were injected intra-peritoneally with an extract obtained from diesel oil-based drilling mud. Fish were exposed to different doses of extracts (made up to 2.4 mL/kg with olive oil), i.e. 0, 0.6, 1.2 and 2.4 mL/kg body weight (B.W.), for 6 weeks in the dose effect experiment.