SPONTANEOUS CYTOTOXICITY OF CULTURED HUMAN CELL LINES MEDIATED BY NORMAL PERIPHERAL-BLOOD LYMPHOCYTES .3. KINETIC-PARAMETERS

  • 1 January 1978
    • journal article
    • research article
    • Vol. 121  (2) , 710-717
Abstract
The mechanism of spontaneous cell-mediated cytotoxicity (SCMC) of cultured cell lines was investigated and compared with antibody-dependent cell-mediated cytotoxicity (ADCMC) by detailed kinetic analysis. The mechanism of SCMC resembles that of an enzyme, as does ADCMC where effector cells are analogous to an enzyme and the 51Cr-labeled target cells are analogous to the substrate. Temporal kinetic studies revealed an induction period of about 1 h before significant 51Cr release for SCMC, but not for ADCMC. This induction period is not due to differences in effector-target affinity between SCMC and ADCMC. Kinetic analysis showed that SCMC approaches simple Michaelis-Menten enzyme kinetics, allowing determination of Km and Vmax for the interaction between a given effector and target cell. The Km values thus determined were identical for the lysis of several target cell lines of varying SCMC susceptibility to effector cells from a given donor, whereas Vmax values for lysis of different target cells varied considerably. Effector cells isolated from the peripheral blood of different donors exhibited different Km values for the target cells tested. The Km value obtained for ADCMC effected by a given donor''s lymphocytes was equal to the Km value obtained for SCMC by that donor.