Molecular cloning and phylogenetic analysis of beluga whale (Delphinapterus leucas) and grey seal (Halichoerus grypus) interleukin 2

Interleukin 2 (IL-2) is a lymphokine produced by activated T helper lymphocytes which exerts immunoregulatory effects on a variety of immune cells, including T cells, activated B cells, natural killer cells, and lymphokine-activated killer cells. In this study, we cloned and determined the entire beluga whale (Delphinapterus leucas) and grey seal (Halichoerus grypus) IL-2-encoding cDNA sequences, and analysed their genetic relationships with those from several mammalian species obtained from the Genbank Database. The encoding nucleic acid sequences of beluga whale and grey seal IL-2 were 465 and 468 bp in length, respectively. The identity levels of IL-2 nucleic and deduced amino acid sequences from the beluga whale and grey seal with those from the other mammalian species, ranged from 59.9% to 89.5%, and 52.9% to 77.3%, and from 61.1% to 93.2%, and 58.7% to 88.4%, respectively. Phylogenetic analysis based on both nucleic and amino acid sequences showed that the beluga whale IL-2 was closely related to that of the ruminant species, which includes the bovine, while the grey seal IL-2 was closely related to that of the canine.