Effect of in vitro cadmium exposure on natural killer (NK) cells of catfish, ictalurus melas

The effect of in vitro cadmium exposure on catfish natural killer (NK) cells was investigated. Purification of NK cells by nylon-wool columns and density gradient centrifugation indicated that they were a population of nylon-wool adherent cells. Subsequently NK cells were separated only by density gradient centrifugation, where these cells band at the 43/45·5% Percoll interface. In some cytotoxicity assays, catfish NK cells were exposed to 5, 10, 30 and 50 μM cadmium (CdCl₂); 10 μl of Cd solutions were added to NK cells simultaneously with the target cells. In vitro, 5 μM Cd inhibited the ability of catfish NK cells to kill the human erythroleukemic cell line K-562. In the presence of 10 μM Cd, the antibody-independent cytotoxic activity was totally suppressed.