Natural Killer (NK) Cell Assays in Immunotoxicity Testing.

It is well known that natural killer (NK) cells are involved in defense against viruses and some tumors. NK cells kill target cells by the directed release of cytolytic granules that contain perforin, granzymes, and granulysin. It is increasingly important to evaluate NK cell function in immunotoxicity testing. NK cell function can be evaluated by determining cytolytic activity against target tumor cells by the 51Cr-release assay and also by determining the number of NK cells in peripheral blood in humans and in the spleen in animals using flow cytometry. Recently, the intracellular levels of perforin, granzymes, and granulysin determined by flow cytometry have also been used in the evaluation of NK cell function. In addition, chemical-induced apoptosis in NK cells also has been applied to evaluate the immunotoxicity of chemicals. This chapter will describe the methods for NK cell assays in immunotoxicity testing.