Measuring the activity of cytolytic lymphocytes

The protocols in this unit describe how to measure the activity of the two most common types of lymphocytes that have cytolytic activity: cytotoxic T lymphocytes (CTL) and natural killer (NK) cells. Measurement of CTL activity requires priming of cells, which can be performed either in vivo or in vitro. Priming leads to a population of differentiated, antigen-specific CTL. Protocols in which CTL are primed in vivo and in vitro are included in this unit. In contrast to CTL, the cytolytic activity of NK cells can be measured in the absence of antigen priming. In all of these protocols, single-cell suspensions of effector and target cells are prepared separately. The target cells are labeled with (51)Cr, and then the effector and target cells are co-cultured for several hours. The amount of target cell lysis is determined by measuring the amount of (51)Cr released into the culture medium. For all of the protocols, the effector cells are derived from mouse spleen. The target cells are either spleen cells from mice of a different MHC haplotype, virus-infected cells, tumor cells, or cultured cell lines. These protocols provide a methodological framework that can be adapted for measuring the activity of cytolytic lymphocytes in a variety of experimental paradigms.