Simultaneous Determination of the Concentration and Lytic Activity of Effector Cells that Mediate Natural and Antibody-Dependent Cytotoxicity

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Abstract
Cellular cytotoxicity reactions can be studied in a manner analogous to that used to measure enzyme activity. This approach yields 2 parameters: Vmax, the maximal rate of target cell lysis that can be achieved by the lymphocyte preparation tested; and, KMapp, the apparent Michaelis constant. By analogy to many enzyme-catalyzed reactions KMapp values for cytotoxicity reactions have generally been interpreted in terms of dissociation constants for the interaction of receptor sites on effector cells with antigens on the target cells. Experimentally determined KMapp values for natural or antibody-dependent cytotoxicity reactions are approximately equal to the concentration of [human] NK [natural killer] or K [antibody-dependent killer] effector cells in the lymphocyte preparation tested. This result makes possible the simultaneous determination of both effector cell frequency and lytic activity in a given lymphocyte preparation.