The mechanism of natural killer (NK) cell-mediated cytotoxicity was investigated by examining the susceptibility of NK target cells to lysis by soluble mediators. Evidence is presented that demonstrates that mediators released from a nonimmune effector population can selectively lyse NK target cells. A miniaturized Marbrook culture system was adapted to assay for soluble mediators. Effector cells cultured in the bottom well stimulated with PHA, Con A, or PHA-coated L929 fibroblasts released soluble mediators cytotoxic to NK target cells cultured in the top chamber. These mediators required an incubation period of 40 hr to cause significant target cell lysis as measured by trypan blue exclusion. Soluble mediators released from murine spleen cells lysed the NK-sensitive YAC-1 and RL♂1 targets but not the NK-insensitive P815, EL4, AKSL2, LA-6, or YAC and RL♂1 passaged in vivo. Human peripheral blood lymphocytes released mediators cytotoxic to the NK-sensitive K562 and Molt-4 target cells but not to the NK-insensitive Raji or IM-9 targets. The soluble mediator was released from cultures of spleen cells of various mouse strains, including the nude mouse, but not from thymocytes. Cellfree supernatants derived from spleen cell cultures could lyse NK targets when assayed in the Marbrook system. Studies with these supernatants containing the soluble mediator revealed that a) the m.w. of the mediator was greater than 12,000, b) it was stable at −20°C but was inactivated by heating at 100°C for 15 min, and c) its lytic activity was inhibited by the addition of α-methyl-d-mannoside, d-galactose, or N-acetyl-d-galactosamine at 25 to 50 mM. The relationship of the soluble mediator, conventional lymphotoxins, and the mechanism of lysis in direct NK CMC reactions is discussed.
No takes yet. Share an insight, caveat, or question.
Wright et al. (1981) studied this question.