Immunosuppression in mice fed on diets containing beluga whale blubber from the St Lawrence Estuary and the Arctic populations

In order to assess the immunotoxic potential of naturally relevant mixtures of PCBs and other organohalogens, C57B1/6 mice were fed on diets in which lipids were replaced by blubber of beluga whales from the highly contaminat ed population of the Saint-Lawrence River, and the less contaminated popula tion from the Arctic. Different ratios of blubber from both sources were mi xed in order to allow a dose-response study. Mice were fed for a period of 90 days at the end of which their immunological status was monitored. For g eneral parameters such as body weight, weight of the spleen and the thymus no significant effect of diets were observed. The immunological endpoints s uch as the blastic tranformation of splenocytes and the spleen NK cell acti vity were not significantly affected by any of the diets compared to contro l diets. While the different cell subpopulations of peripheral blood and th ymus were not affected by the diets, a significant decrease was noted in th e CD8 + T cell population in the spleen of mice fed with most of the diets containing beluga blubber. Moreover, the ability of splenic cells to elicit humoral response against sheep red blood cells as well as the potential of peritoneal macrophages to perform phagocytosis were suppressed by all diet s containing beluga blubbers. In summary, there was no differences between the groups fed with a blubber diet with low and high organochlorine contami nation. However, a clear immunosuppression was demonstrated when these grou ps were compared to the group fed with beef oil. Despite the fact that we c annot exclude a possible contribution of the fatty acid composition of the beluga blubber to the immunosupression, these results suggest the sensitivi ty of mouse immune system towards organohalogens, and point out the toxic p otential of contaminant mixtures as found in the less contaminated Arctic p opulation. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.