Measurements of Natural Killer (NK) Activity and NK-Cell Quantification.

Natural killer (NK) cells are a subset of lymphocytes with a distinct morphology and the ability to kill certain target cells via one or more cytolytic mechanisms. Measurements of in vitro NK activity from heparinized whole blood, or lymphocytes isolated from human peripheral blood or tissue, may be performed by a variety of techniques. Procedures using standard 51Cr-release assays as well as nonradioactive labeling materials are described in detail in this article, and advantages and disadvantages of these methods are discussed.