Roozemond R C, Bonavida B
J Immunol. 1985 Apr;134(4):2209-14.
NK cell-mediated cytotoxicity results from membrane interactions between NK effector and target cells. The role of membrane fluidity in these events is not known. The present study was undertaken to investigate the effect of changes in membrane lipid fluidity of NK effector and NK-sensitive target cells on the lytic pathway of NK cell-mediated cytotoxicity. Fluidity was modulated by various lipids and measured by fluorescence polarization. NK effector cells treated with phosphatidylcholine complexed with polyvinylpyrrolidone (PVP) and bovine serum albumin (BSA) showed increased membrane fluidity. This fluidization of the effector cell membrane resulted in a significant inhibition of cytotoxic activity in the 51Cr-release assay. Single cell analysis revealed that the inhibition was due to a decrease in the frequency of NK target conjugates and reduced killing of conjugated targets. Rigidification of the NK effector cell membranes by treatment with cholesteryl hemisuccinate complexed with PVP and BSA also resulted in inhibition of cytotoxicity. This inhibition was post binding, because binding was increased and lysis was abrogated. Fluidization of K562 target cell membranes caused a slight but insignificant increase in their lysis by NK cells without affecting the binding step. On the other hand, rigidification of K562 membranes decreased the sensitivity of these target cells to lysis. Single cell analysis revealed that this inhibition of NK lysis is post binding, because the frequency of killers was significantly decreased. It was also shown that membrane rigidification of target cells that were programmed for lysis during the lethal hit stage and subsequently separated from effector cells, rendered the programmed cells resistant to killing during the killer cell-independent lysis step. These results demonstrate that fluidization or rigidification of the plasma membrane of either effector or target cells affect different stages of the NK cell-mediated cytolytic events.
自然杀伤（NK）细胞介导的细胞毒性源于NK效应细胞与靶细胞之间的膜相互作用。膜流动性在这些过程中的作用尚不清楚。本研究旨在探讨NK效应细胞和NK敏感靶细胞膜脂质流动性变化对NK细胞介导的细胞毒性裂解途径的影响。通过各种脂质调节流动性，并通过荧光偏振进行测量。用与聚乙烯吡咯烷酮（PVP）和牛血清白蛋白（BSA）复合的磷脂酰胆碱处理的NK效应细胞显示膜流动性增加。效应细胞膜的这种流化导致在51Cr释放试验中细胞毒性活性的显著抑制。单细胞分析表明，这种抑制是由于NK靶细胞结合物的频率降低以及结合靶细胞的杀伤减少。用与PVP和BSA复合的胆固醇半琥珀酸酯处理使NK效应细胞膜僵化，也导致细胞毒性受到抑制。这种抑制是在结合后发生的，因为结合增加而裂解被消除。K562靶细胞膜的流化导致NK细胞对其裂解略有增加但不显著，且不影响结合步骤。另一方面，K562膜的僵化降低了这些靶细胞对裂解的敏感性。单细胞分析表明，NK裂解的这种抑制是在结合后发生的，因为杀伤细胞的频率显著降低。还表明，在致死性打击阶段被编程裂解并随后与效应细胞分离的靶细胞膜僵化，使编程细胞在不依赖杀伤细胞的裂解步骤中对杀伤具有抗性。这些结果表明，效应细胞或靶细胞的质膜流化或僵化会影响NK细胞介导的溶细胞事件的不同阶段。
