Immune functions in beluga whales (Delphinapterus leucas): evaluation of natural killer cell activity

Natural killer (NK) activity, an important non-specific defense mechanism against viral infections and tumors, was demonstrated in beluga whales using two different methods: 51Cr release and flow cytometry. Using the 51Cr release assay, NK activity in belugas was shown to be higher against K-562 than against YAC-1 cell lines. Moreover, it was enhanced by the addition of human recombinant interleukin-2 with both cell lines. NK activity evaluated by flow cytometry in the peripheral blood of eight belugas increased when the effector:target cell (E:T) ratio increased, and averaged 13.9% +/- 3.8% (range 9.9% to 17.8%) at an E:T ratio of 100:1. While NK activity could be readily detected using both methods, the lack of radio-isotopes and related laboratory room make the flow cytometric method a viable and safe alternative. The evaluation of this function in cetaceans could lead to a better understanding of the early events that lead to viral epizootics in populations of marine mammals in different parts of the world, as well as to the high prevalence of neoplasms in St. Lawrence beluga whales.