Comparative Evaluation of Natural Killer Cell-mediated Cell Killing Assay Based on the Leakage of an Endogenous Enzyme or a Pre-loaded Fluorophore.

A cell-killing ability of natural killer (NK) cells has been evaluated by the leakage of marker molecules from target cells. Lactate dehydrogenase (LDH) and calcein are two major non-radioisotope markers used for the killing assay. The spontaneous death of NK cells during the killing-assay of cells is a major issue in the assay because it provides background signals to increase errors.