Evidence of a dynamic role of the target cell membrane during the early stages of the natural killer cell lethal hit.

The role of membrane movement during the stages of human NK cytolysis has been examined by using the bifunctional protein cross-linking reagent, glutaraldehyde. The binding stage was inhibited when K562 target cells or NK cells were pretreated with glutaraldehyde. When added post-binding, after initiation of calcium pulse, glutaraldehyde did not dissociate conjugates, but inhibited NK cytolysis. In contrast to the early stages of NK cytolysis, glutaraldehyde enhanced lysis during the terminal stage, killer cell independent lysis ( KCIL ). Lysis of the preprogrammed target cells, however, was enhanced only when glutaraldehyde was added immediately after dispersion of the conjugates, before target cell lysis. The mechanism of enhancement of lysis during the terminal stages of cytolysis was further explored in assays for NK cell-derived cytolytic factor (NKCF). L929 target cells prebound with NKCF were lysed more readily in the presence of glutaraldehyde, but as in KCIL , maximum enhancement of lysis occurred when glutaraldehyde was added immediately after NKCF was bound to the target cell. These results suggest that the target cell membrane may play a dynamic role during the terminal stages of the NK lethal hit.