Sequential substages of natural killer cell-derived cytolytic factor (NKCF)-mediated cytolysis as defined by glutaraldehyde modulation of the target cell.

The substages of natural killer cell-derived cytolytic factor (NKCF)-mediated cytolysis have been examined by using the bifunctional protein cross-linking reagent glutaraldehyde. Glutaraldehyde (2 X 10(-4%)) enhanced both the level and rate of lysis mediated by NKCF when the factor was prebound to the L929 target cell. However, glutaraldehyde enhanced lysis only when added at specific time points (2 to 4 hr after addition of NKCF, which was 6 to 8 hr before any lysis occurred), indicating that NKCF-mediated lysis is a dynamic process. When 10(-3%) glutaraldehyde was added at the same time as NKCF, inhibition of lysis was observed. Pretreatment of L929 target cells, but not of NKCF, with glutaraldehyde resulted in inhibition of NKCF-mediated cytolysis. In addition, it was shown that glutaraldehyde-pretreated L929 and K562 cold target cells were not as effective in competing for binding of NKCF in a cold target competition assay, or as effective in absorbing NKCF at 4 degrees C, indicating that glutaraldehyde modified the NKCF receptor to block binding of NKCF to the target cell. Thus, NKCF-mediated cytolysis can be divided into at least four substages based upon sequential modulation by glutaraldehyde: 1) NKCF binding stage (inhibited by glutaraldehyde), 2) glutaraldehyde-enhanceable nonlytic stage, 3) glutaraldehyde-nonenhanceable nonlytic stage, and 4) glutaraldehyde-nonenhanceable lytic stage.