Quantitative measurement of apoptosis induced by cytotoxic T lymphocytes.

Cytotoxic T lymphocytes destroy virus-infected and malignant cells through the induction of apoptosis. This form of cell death is characterized by a number of cellular changes including cell shrinkage and membrane blebbing, chromatin condensation and DNA fragmentation, externalization of phosphatidylserine to the outer leaflet of the plasma membrane, and disruption of the inner mitochondrial transmembrane potential (delta psi m). Cell death induced by cytotoxic T lymphocytes is associated with similar morphological and biochemical features. Here we demonstrate how methods typically employed to detect apoptotic cells can be adapted to monitor cell death mediated by cytotoxic T lymphocytes. We have specifically selected techniques that allow quantitative evaluation of death including membrane changes, DNA fragmentation, and mitochondrial depolarization.