Regulation Of Natural Killer Cell Activity

自然杀伤(NK)细胞是除B细胞和T细胞外的第三种淋巴细胞亚型。NK细胞在抵御病毒和其他细胞内病原体方面具有重要的免疫功能。与B和T细胞不同，NK细胞不表现出对抗原的特异性，因此得名，因为它们可以在没有抗原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可以阻止对正常健康细胞的杀伤。已有大量受体被描述为激活NK细胞的细胞毒反应。然而，目前还不清楚这些受体中的任何一个是否足以和/或必须激活自然的细胞毒作用。这个项目的主要目标是确定NK细胞激活的分子基础，并表征涉及的受体。已经开发了一种重建系统来测试单个受体对激活NK细胞细胞毒的贡献。为了确定激活NK细胞细胞毒作用的条件，在昆虫细胞系中表达了几种NK细胞受体的特异性配体。令人惊讶的是，仅ICAM-1的表达就足以诱导昆虫细胞的溶解，这表明整合素LFA-1不仅对于NK细胞与靶细胞的黏附是必不可少的，而且对于传递激活信号也是必不可少的。其他NK细胞激活受体(如CD16、CD2和2B4)的配体表达不足以诱导细胞毒作用，但与ICAM-1共表达确实增强了ICAM-1单独诱导的细胞裂解。对静息NK细胞效应功能的调节还不是很清楚。昆虫细胞系统表明，即使在没有细胞因子或趋化因子的情况下，CD2和2B4受体与靶细胞的结合也会导致强烈的粘附力增强。NK细胞受体KIR2DL4具有诱导干扰素-γ产生的独特特性，但在没有细胞因子的情况下，通过静息NK细胞而不产生细胞毒性。DNA微阵列研究以及随后的蛋白质分析显示，KIR2DL4结扎诱导了促炎反应。此外，KIR2DL4携带一种不同寻常的结构元素组合，使其具有激活和抑制潜力。

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.