Assays of natural killer (NK) cell ligation to target cells

The formation of a conjugate between an effector lymphocyte and a target cell is the first step in cellular cytotoxicity reactions. This protocol, previously known as the “binding assay,” measures the ability of different lymphoid cell populations to adhere to a tumor target cell. In particular, it is used to monitor the formation of conjugates in vitro between natural killer (NK) cells and susceptible target cells (e.g., K562 cells for human NK, YAC cells for mouse NK) based on side-scatter signals, and it allows discrimination between effector and target cells based on detection of effector cell–specific antigens using fluorochrome-conjugated monoclonal antibodies.