An isolated population of around 500 beluga whales (Delphinapterus leucas) reside in the St. Lawrence Estuary. They have been found to be highly contaminated by many industrial and agricultural contaminants, among which PCBs and DDT are probably the most important. Also, necropsies of these animals have shown a variety of lesions, including many infections with opportunistic bacteria, and a high prevalence of neoplasms. Immunosuppression associated with the contaminants present in the tissues of these animals has been proposed to explain the amount of lesions found.

An immunotoxicological evaluation of highly contaminated St. Lawrence beluga whales compared to much less contaminated Arctic belugas was started, and tests have been set to evaluate some immune functions in this species. Frozen leucocytes from belugas captured in Churchill, Manitoba, as well as fresh blood from captive belugas at John G. Shedd Aquarium in Chicago, were used to adapt tests for belugas. Mitogen-induced lymphoblastic transformation using four different lectins (Con-A, PHA, LPS and PWM) were run with different concentrations of those lectins to define a standard curve. This test is useful to evaluate the ability of lymphocytes to divide when stimulated. Flow cytometry was used to evaluate phagocytosis of fluorescent latex beads by polymorphonuclear cells and monocytes. Respiratory burst of PMA-stimulated leucocytes was also evaluated using flow cytometry. Phagocytosis represents the ability of leucocytes, primarily polymorphonuclear cells, to ingest foreign particles, and respiratory burst represents their efficacy to destroy those particles; these two functions are the first lines of defense of an organism. NK function, mixed lymphocytes reaction and immuno-histochemical staining properties of beluga whale leucocytes are currently investigated. With these immunological tests, along with the analysis of the toxic compounds found in the serum and blubber of St. Lawrence and Arctic beluga whales, we will try to demonstrate a relation between the contamination and a possible immunosuppression in these animals.