Non-specific cytotoxic activity of teleost leukocytes

The existence of lymphoid cells with "natural" killer activity in mammals and birds has been known for some time. Several previous reports have demonstrated similar activity in carp and catfish kidney leukocytes. However, the activity previously reported was directed towards established mammalian cell lines. In this report we confirm the existence of spontaneous killer activity in other species of teleosts, including salmonids. This spontaneous cytotoxic activity is directed towards several established teleost, as well as mammalian, cell lines. Cytotoxic activity appears to be optimal at 20 degrees C in an 8 hour 51Cr release assay. The RTG-2, AS, GS and EPC cell lines of teleost origin are susceptible to lysis by kidney, spleen, and blood leukocytes of Salmo salar, Salmo gairdneri, and Notemigonus crysoleucas. Furthermore, the susceptibility of the RTG-2 and AS teleost cell lines to killing by kidney leukocytes of both S. salar and S. gairdneri was significantly enhanced by preinfection of the target cells with infectious pancreatic necrosis virus.