Regulation Of Natural Killer Cell Activity

自然杀伤（NK）细胞是除B和T细胞之外的第三种淋巴细胞亚型。NK细胞在防御病毒和其他细胞内病原体方面提供重要的免疫功能。与B和T细胞不同，NK细胞对抗原不表现出特异性，它们之所以得名是因为它们可以在没有抗原的预先刺激的情况下杀死细胞。NK细胞上识别主要组织相容性I类分子的抑制性受体阻止了对正常健康细胞的杀伤。已经描述了大量激活NK细胞的细胞毒性应答的受体。然而，尚不清楚这些受体中的任何一种是否足以和/或必需激活天然细胞毒性。该项目的主要目标是确定NK细胞活化的分子基础和表征所涉及的受体。已经开发了一种重建系统来测试单个受体对NK细胞细胞毒性活化的贡献。在昆虫细胞系中表达NK细胞受体的几种特异性配体，以确定NK细胞细胞毒性活化的要求。令人惊讶的是，ICAM-1单独的表达足以诱导昆虫细胞的裂解，这表明整联蛋白LFA-1不仅对于NK细胞与靶细胞的粘附是必需的，而且对于传递活化信号也是必需的。其他NK细胞活化受体（如CD 16、CD 2和2B 4）的配体表达不足以诱导细胞毒性，但与ICAM-1共表达确实增强了ICAM-1单独诱导的溶解。静息NK细胞中效应子功能的调节还不清楚。使用昆虫细胞系统来显示受体CD 2和2B 4通过其各自的配体在靶细胞上的接合导致粘附的强烈增强，即使在不存在细胞因子或趋化因子的情况下。NK细胞受体KIR 2DL 4具有在不存在细胞因子的情况下通过静息NK细胞诱导干扰素-γ产生而非细胞毒性的独特性质。DNA微阵列研究，随后进行蛋白质分析，揭示了KIR 2DL 4连接诱导促炎反应。此外，KIR 2DL 4携带一种不寻常的结构元件组合，赋予其激活和抑制潜力。

Natural killer (NK) cells are a third subtype of lymphocytes besides B and T cells. NK cells provide an important immune function in the defense against viruses and other intracellular pathogens. Unlike B and T cells, NK cells do not exhibit specificity for antigen and they acquired their name because they can kill cells without prior stimulation by antigen. The killing of normal healthy cells is prevented by inhibitory receptors on NK cells that recognize major histocompatibility class I molecules. A large number of receptors that activate the cytotoxic response of NK cells have been described. However, it is not clear if any one of these receptors is sufficient and/or necessary to activate natural cytotoxicity. The major goal of this project is to define the molecular basis of NK cell activation and to characterize the receptors involved. A reconstitution system has been developed to test for the contribution of individual receptors to the activation of NK cell cytotoxicity. Several specific ligands of NK cell receptors were expressed in an insect cell line in order to define the requirements for activation of NK cell cytotoxicity. Surprisingly, expression of ICAM-1 alone was sufficient to induce lysis of the insect cells, suggesting that the integrin LFA-1 is essential not only for adhesion of NK cells to target cells, but also for transmitting activation signals. Expression of ligands for other NK cell activation receptors (such as CD16, CD2, and 2B4) was not sufficient to induce cytotoxicity but co-expression with ICAM-1 did enhance the lysis induced by ICAM-1 alone. The regulation of effector functions in resting NK cells is not well understood. The insect cell system was used to show that engagement of receptors CD2 and 2B4 by their respective ligand on target cells resulted in a strong enhancement of adhesion, even in the absence of cytokines or chemokines. The NK cell receptor KIR2DL4 has the unique property of inducing interferon-gamma production, but not cytotoxicity, by resting NK cells in the absence of cytokines. A DNA microarray study, followed by protein analysis, revealed that KIR2DL4 ligation induces a pro-inflammatory response. Furthermore, KIR2DL4 carries an unusual combination of structural elements that endow it with both activating and inhibitory potential.