Effects of Polymorphism on Levels of KIR Expression

自然杀伤(NK)细胞是一种具有天然免疫功能的淋巴细胞，在感染早期分泌细胞因子并杀死细胞。除了抵抗感染，NK细胞还控制着孕期植入过程中滋养细胞的侵袭，并能介导异基因骨髓移植后的移植物抗白血病反应。NK细胞的反应受激活和抑制受体系统的控制，其中一些受体识别MHC I类或L类配体。其中，杀伤细胞免疫球蛋白样受体(KIR)高度多样化，进化迅速，识别多态的HLAI类分子。虽然KIR系统在小鼠身上是退化的，但在人类物种中是高度复杂的。值得注意的是，KIR基因座的端粒部分包含高度多态的KIR3DL1和KIR3DL2基因，与其他灵长类物种相比，人类的端粒部分是扩大的。KIR3DL1编码人类白细胞抗原B特异性抑制受体 决定因素。KIR3DL1的同种异型是通过它们在细胞表面的表达水平来区分的，这种对数量级的调制被认为是多态的主要功能。三个目标将共同检验这一假设。在目标1中，将通过比较自然发生的同种异型和自然发生的替换被交换的突变体来研究蛋白质多态在设定细胞表面水平中的作用。分析将使用一种新开发的方法来量化细胞表面存在的细胞KIR3DL1的相对数量。目的2研究KIR3DL1基因启动子和其他非编码多态对KIR3DL1表面水平的影响 表情。因此，目标1和目标2将定义为14个KIR3DL1异型中的每一个设定表面表达水平的精确机制。目的研究在不改变KIR3DL1蛋白序列的情况下，改变KIR3DL1的表达水平对NK细胞功能的影响。这将把多态的其他潜在影响从细胞表面的表达水平中分离出来，例如配体专一性。

Natural killer (NK) cells are lymphocytes of innate immunity that secrete cytokines and kill cells at early times of infection. Besides defending against infection, NK cells also control trophoblast invasion during implantation in pregnancy and can mediate graft-versus-leukemia responses following allogeneic bone-marrow transplantation. NK-cell responses are controlled by systems of activating and inhibitory receptors, some of which recognize MHC class I or class l-like ligands. Of these, the killer-cell immunoglobulin-like receptors (KIR) are highly diverse, rapidly evolving and recognize polymorphic HLA class I molecules. Although vestigial in mice, the KIR system is highly elaborated in the human species. Notably, the telomeric part of the KIR locus, which contains the highly polymorphic KIR3DL1 and KIR3DL2 genes, is expanded in humans compared to other primate species. KIR3DL1 encodes inhibitory receptors specific for HLA-B determinants. Allotypes of KIR3DL1 are distinguished by their levels of expression at the cell surface, a modulation over an order of magnitude that is proposed to be a main function of the polymorphism. Three aims will work together to test this hypothesis. In aim 1, the role of protein polymorphism in setting cell surface levels will be investigated by comparison of naturally occurring allotypes and mutants in which the naturally occurring substitutions are swapped. Analysis will use a newly developed assay for quantifying the relative amount of cellular KIR3DL1 that is present on the cell surface. Aim 2 will investigate the influence of promoter and other non-coding polymorphisms of the KIR3DL1 gene upon the surface level of KIR3DL1 expression. Thus aims 1 and 2 will define the precise mechanisms that set the level of surface expression for each of fourteen KIR3DL1 allotypes. Aim 3 will investigate the effects on NK-cell functions of changing the levels of KIR3DL1 expression in the absence of change in the protein sequence. This will separate other potential effects of the polymorphism, such as ligand specificity, from the level of cell-surface expression.