ANTIBODY-INDUCED APOPTOSIS IN A HUMAN LEUKEMIA-CELL LINE IS ENERGY-DEPENDENT - THERMOCHEMICAL ANALYSIS OF CELLULAR-METABOLISM

The mouse monoclonal anti-BAL antibody induced apoptosis in a pre-B ac ute lymphocytic leukemia cell line within 2 days of incubation, after being crosslinked by a secondary antibody. The antibody specifically r ecognized a 37 kDa membrane protein that was expressed on a wide spect rum of normal and malignant cells, but induced programmed cell death i n only very few of these cells. In this study, we have followed the in itial kinetics of the antibody-induced cell death in the human acute l ymphocytic leukemia cell line KM-3, by microcalorimetric measurements in conjunction with determination of the cellular proliferation rate a nd DNA fragmentation. An increase in metabolic activity was observed a lready after incubating the cells for 20 min with crosslinked anti-BAL antibody, which was several hours before significant growth inhibitio n and DNA fragmentation were detected. These data show for the first t ime that the initiation phase of antibody-induced apoptosis is an acti ve, energy-dependent process and not merely an effect of receptor bloc king.