CHANGES IN ACTIN ORGANIZATION DURING THE CYTOTOXIC PROCESS

Changes in organization of F-actin during the cytotoxic process betwee n NK and K562 cells have been observed and studied using confocal lase r scanning microscopy and quantitative fluorescence microscopy. An inc rease in F-actin content and orientation of F-actin towards the target cell have been observed in conjugated NK cells. The increase in F-act in content probably reflects activation of the NK cell for the killing process. An increase in F-actin content in the conjugated K562 cell, occurring simultaneously with the appearance of filamentous actin stru ctures that often originated/ended at the contact place with the NK ce ll, was also observed. These changes were delayed compared to the incr ease in F-actin content in the NK cell and were accompanied by increas ing cytotoxic activity. This indicates that they were results of the i nteraction of the K562 cell with the activated NK cell. The possible r ole of target cell micro filaments in the cytotoxic process is address ed. (C) 1994 Wiley-Liss, Inc.