Increased osmolarity with low molecular weight solutes inhibits CTL-mediated cytotoxicity

Sucrose induced hyperosmolarity, which has no effect on complement-mediated lysis, was examined for its effect on CTL-mediated cell lysis. Sucrose (0.15M) inhibited H-2/sup b/ anti-H-2/sup d/ PEL specific lysis, as measured by 51Cr-release, 82.7% (52 +/-1.4 vs. 9 +/- 0.6). The effect of sucrose on the killer cell independent phase was investigated by allowing the killers and targets to interact for 10 minutes at 370C, and then inactivating the killers by a 5 minute incubation at 440C before adjusting the osmolarity. Under these conditions killing was reduced 65.5% (58 +/- 0.5 vs. 20 +/- 0.8) when hit P815 target cells were incubated in 0.15M sucrose; thus indicating inhibition was at the level of the target cell. This effect was not limited to sucrose as Na2SO4 (.08M) also inhibited 51Cr-release. Nuclear fragmentation as indicated by release of incorporated 3H-thymidine also was inhibited in the presence of high osmolarity, although to a lesser extent, 34% (47 +/- 1.6 vs 31 +/- 0.6) after 40 minutes. These data suggest a surprising difference between poly C9 and CTL polyperforins, in light of their reported homologies