Activation of Human Natural Killer Cell Function

在2013财年我们完成了几个目标后，这个项目采取了新的方向。我们正在定义激活NK细胞增殖的最低要求，使用在以前的项目中已经成功的方法。白介素15(IL-15)是NK细胞生存和增殖所必需的。与其他可溶的细胞因子不同，IL-15与IL-15受体(IL-15R)的阿尔法链结合。IL-15Rα-IL-15复合体不在NK细胞上表达，而是在其他细胞上表达，它将IL-15转运到NK细胞上表达的IL-15R的β链和伽马链上。然后，IL-15Rβ/伽马复合体向NK细胞传递信号，以求生存、增殖和转录一组特定的基因。在免疫突触的背景下反式呈现IL-15开启了NK细胞增殖信号可能受到其他受体-配体相互作用的调节的可能性。利用单独或与其他NK受体配体结合的IL-15Rpha转基因昆虫细胞，我们已经证明，IL-15的反式递送独立于通过整合素的黏附和通过其他激活受体的信号传递。IL-15Rpha链也与作为抑制性受体配体的HLAI类分子结合在一起在人类细胞系上表达。这个系统模拟了人类细胞对IL-15的反式递送，这种反式递送发生在人类白细胞抗原I类分子的背景下。我们已经证明，IL-15反式递呈诱导的NK细胞的增殖是由抑制性受体同时参与调节的。这种抑制发生在促进增殖的信号水平上，但转录依赖于Stat5的信号不受影响。

After completion of several of our objectives in FY13, this project has taken a new direction. We are defining the minimal requirements for the activation of NK cell proliferation, using approaches that have been successful in previous projects. The interleukin 15 (IL-15) is essential for NK cell survival and proliferation. Unlike other cytokines, which are soluble, IL-15 is bound to the alpha chain of the IL-15 receptor (IL-15R). The IL-15Ralpha-IL-15 complex is not expressed on NK cells but on other cells, which trans-present IL-15 to the beta and gamma chains of the IL-15R expressed on NK cells. The IL-15Rbeta/gamma complex then transmits signals to the NK cell for survival, proliferation, and transcription of a specific set of genes. Trans-presentation of IL-15 in the context of an immunological synapse opens the possibility that signaling for NK cell proliferation may be subject to regulation by other receptor-ligand interactions. Using insect cells transfected with IL-15Ralpha, either alone or in combination with ligands for other NK receptors, we have shown that IL-15 trans-presentation occurs independently of adhesion through integrin, and of signaling by other activation receptors. The IL-15Ralpha chain was also expressed on a human cell line in combination with HLA class I molecules that serve as ligands for inhibitory receptors. This sytem mimics IL-15 trans-presentation by human cells, which occurs in the context of HLA class I molecules. We have shown that the proliferation of NK cells induced by IL-15 trans-presentation is modulated by the simultaneous engagement of inhibitory receptors. The inhibition occurs at the level of the signals that promote proliferation, but that the Stat5-dependent signals for transcription are not affected.