Investigating links between polychlorinated biphenyl (PCB) exposure and thymic involution and thymic cysts in harbour porpoises (Phocoena phocoena).
The associations between polychlorinated biphenyls (PCBs) exposure and involution of lymphoid tissue and development of epithelial-lined cysts in the thymus of UK-stranded harbour porpoises (Phocoena phocoena) (n=170) were tested. Percentage of thymic lymphoid tissue (%TLT) was histologically quantified. Multiple regression analyses (n=169) demonstrated significant positive correlation between %TLT and nutritional status (p<0.001) and significant negative association between %TLT and onset of sexual maturity (p<0.001). However, in a subgroup of porpoises with total PCB levels above a proposed threshold of toxicity (>17mg/kg lipid weight) (n=109), the negative association between %TLT (as dependent variable) and summed blubber concentrations of 25 chlorobiphenyl congeners (∑25CBs) remained significant (p<0.01) along with nutritional status (p<0.001) and onset of sexual maturity (p<0.001). These results suggest PCB-induced immuno suppression may be occurring in harbour porpoises in UK waters but only at concentrations that exceed proposed toxicity thresholds for marine mammals. In contrast, development of thymic cysts appears predominantly age-related.
Institute of Zoology, Zoological Society of London, Regent's Park, NW1 4RY London, UK.
Xinli
X
Yap
Rob
R
Deaville
Matthew W
MW
Perkins
Rod
R
Penrose
Robin J
RJ
Law
Paul D
PD
Jepson
D000818:Animals; D004784:Environmental Monitoring; D005260:Female; D008297:Male; D008476:Mediastinal Cyst / Q000139:chemically induced / Q000453:epidemiology / Q000662:veterinary*; D050741:Phocoena / Q000378:metabolism*; D011078:Polychlorinated Biphenyls / Q000032:analysis / Q000378:metabolism / Q000633:toxicity*; D013950:Thymus Gland / Q000187:drug effects / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000378:metabolism / Q000633:toxicity*
D014874:Water Pollutants, Chemical; D011078:Polychlorinated Biphenyls