Natural killer (NK) cells and cytotoxic T lymphocytes (CTLs) are key elements of the cellular immune response and eliminate pathogen-infected and tumorigenic cells [1–3]. Quantification of killer cell-mediated cytotoxicity is of great importance in immunotherapy [4, 5], to predict cancer risk [6] and to improve antibody-based treatments [7–9]. A precise characterization of killer cell activity is also required to better understand the underlying molecular cytotoxic mechanisms [10–13]. This article is protected by copyright. All rights reserved