Analytical Sciences

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

Kenta TANITO,*1 Yunosuke OSHIRO,*1 Hiroshi TAGAWA,*1 Akihiro KISHIMURA,*1,*2,*3 Takeshi MORI,*1,*2 and Yoshiki KATAYAMA*1,*2,*3,*4,*5

*1 Graduate School of Systems Life Sciences, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
*2 Department of Applied Chemistry, Faculty of Engineering, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
*3 International Research Center for Molecular Systems, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
*4 Center for Advanced Medical Innovation, Kyushu University, 3-1-1 Maidashi, Higashi, Fukuoka 812-8582, Japan
*5 Department of Biomedical Engineering, Chung Yuan Christian University, 200 Chung Pei Road, Chung Li, 32023 ROC, Taiwan

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. In this study, the effect of the spontaneous death of NK cells on the killing assays based on LDH and the calcein method was comparatively evaluated. We found that the calcein method is much less sensitive to the spontaneous death of NK cells to enable an accurate evaluation of the cell killing.

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