Schlichter L, Sidell N, Hagiwara S
Proc Natl Acad Sci U S A. 1986 Jan;83(2):451-5. doi: 10.1073/pnas.83.2.451.
Human natural killer (NK) cells in peripheral blood spontaneously recognize and kill a wide variety of target cells. It has been suggested that ion channels are involved in the killing process because there is a Ca-dependent stage and because killings by presensitized cytotoxic T lymphocytes, which in many respects resembles NK killing, is associated with changes in K and Na transport in the target cell. However, no direct evidence exists for ion channels in NK cells or in their target cells. Using the whole-cell variation of the patch-clamp technique, we found a voltage-dependent potassium (K+) current in NK cells. The K+ current was reduced in a dose-dependent manner by the K-channel blockers 4-aminopyridine and quinidine and by the traditional Ca-channel blockers verapamil and Cd2+. We tested the effects of ion-channel blockers on killing of two commonly used target cell lines: K562, which is derived from a human myeloid leukemia, and U937, which is derived from a human histiocytic leukemia. Killing of K562 target cells, determined in a standard 51Cr-release assay, was inhibited in a dose-dependent manner by verapamil, quinidine, Cd2+, and 4-aminopyridine at concentrations comparable to those that blocked the K+ current in NK cells. In K562 target cells only a voltage-dependent Na+ current was found and it was blocked by concentrations of tetrodotoxin that had no effect on killing. Killing of U937 target cells was also inhibited by the two ion-channel blockers tested, quinidine and verapamil. In this cell line only a small K+ current was found that was similar to the one in NK cells. We could not find any evidence of a Ca2+ current in target cells or in NK cells; therefore, our results cannot explain the Ca dependence of killing. Our findings show that there are K channels in NK cells and that these channels play a necessary role in the killing process. In contrast, the endogenous channel type in the target cell is probably not a factor in determining target cell sensitivity to natural killing.
外周血中的人类自然杀伤（NK）细胞可自发识别并杀死多种靶细胞。有人提出离子通道参与了杀伤过程，这是因为存在一个钙依赖阶段，而且预致敏的细胞毒性T淋巴细胞的杀伤作用在许多方面类似于NK杀伤，它与靶细胞中钾和钠转运的变化有关。然而，目前尚无关于NK细胞或其靶细胞中存在离子通道的直接证据。利用膜片钳技术的全细胞变体，我们在NK细胞中发现了一种电压依赖性钾（K+）电流。钾通道阻滞剂4-氨基吡啶和奎尼丁以及传统的钙通道阻滞剂维拉帕米和Cd2+能以剂量依赖性方式降低K+电流。我们测试了离子通道阻滞剂对两种常用靶细胞系杀伤作用的影响：K562，它源自人类髓系白血病；U937，它源自人类组织细胞白血病。在标准的51Cr释放试验中测定的K562靶细胞的杀伤作用，在与阻断NK细胞中K+电流浓度相当的情况下，被维拉帕米、奎尼丁、Cd2+和4-氨基吡啶以剂量依赖性方式抑制。在K562靶细胞中仅发现一种电压依赖性钠电流，并且它被对杀伤作用无影响的河豚毒素浓度所阻断。U937靶细胞的杀伤作用也被所测试的两种离子通道阻滞剂奎尼丁和维拉帕米所抑制。在该细胞系中仅发现一种小的K+电流，它与NK细胞中的K+电流相似。我们在靶细胞或NK细胞中未发现任何钙电流的证据；因此，我们的结果无法解释杀伤作用对钙的依赖性。我们的研究结果表明NK细胞中存在钾通道，并且这些通道在杀伤过程中起必要作用。相比之下，靶细胞中的内源性通道类型可能不是决定靶细胞对自然杀伤敏感性的因素。
