Role of Killer Immunoglobulin-like Receptor Genes in Aut

自然杀伤(NK)细胞是一组独特的淋巴细胞，通过NK细胞表面一组极其不同的受体识别HLA分子的机制，参与对外来细胞或受感染细胞的监视和杀伤。杀伤免疫球蛋白样受体基因(KIRS)与其他相关基因一起定位于染色体19q13.4。其中一些基因编码识别人类白细胞抗原-C配体的分子，而另一些基因则结合人类白细胞抗原-A和-B分子。与第I类细胞毒性T淋巴细胞(CTL)对肽的识别不同，NK细胞破坏缺乏第I类表达的靶点，并被细胞表面第I类识别所抑制。NK细胞在防御病毒感染细胞和肿瘤细胞方面发挥着重要作用，这些细胞下调I类分子的表达，从而避免CTL的识别。为 例如，HIV-1下调了人类白细胞抗原-A和-B分子(但不是-C)的细胞表面表达，而解释某些人类白细胞抗原类型个体快速发展为艾滋病的一种机制可能涉及NK细胞活性的改变(见项目编号Z01 BC 10269-05LGD)。也有证据表明人类乳头瘤病毒(HPV)下调了I类基因的表达。 KIR基因复合体的单倍型极其多样化，存在的基因数量和类型各不相同，其中一些基因是多态的。我们开发了一种分子分型技术来确定15个KIR基因中每一个的存在或不存在，以研究它们在自身免疫(银屑病关节炎、强直性脊柱炎和多发性硬化症)、感染性疾病(与HIV-1、丙型肝炎病毒和乙肝病毒相关的疾病)和癌症(结直肠癌和宫颈癌)中的潜在影响。初步研究表明，需要定义KIR单倍型的多样性，以便进行与该基因座严格的疾病关联研究。因此，为了确定KIR单倍型及其频率，我们对59个CEPH家族是否存在KIR基因进行了分型，代表了近1,400个KIR单倍型(约370条独立染色体和1,000个减数分裂)。一些KIR基因在几乎所有的KIR单倍型上都能找到，所以当一个亲本有两个基因拷贝(在每条染色体上)而另一个亲本有一个或两个拷贝时，所有的后代都是阳性的，因此无法确定是否有一条染色体缺少该基因位点。在某些情况下，可以通过对该基因中存在的单核苷酸多态进行分型来解决这个问题。因此，我们针对一个常见的KIR基因KIR2DL4设计了一个基于序列的分型系统，并为另一个常见基因KIR3DL1设计了一个SSOP系统。KIR2DL4等位基因分型工作已基本完成，KIR3DL1基因分型工作即将启动。从我们到目前为止收集的数据可以清楚地看出，KIR单倍型是极其复杂的，单倍型变异最明显的机制似乎是不等交换。然而，家族数据并不表明KIR基因复合体内的重组热点。目前正在对这些单倍型进行分型和分析。 NK细胞的活性部分是通过NK细胞上的KIR与它们各自的HLAI类配体之间的相互作用来控制的。鉴于这些分子的功能关系，这两个分子都是由基因组高度多态的非连接区域编码的，因此受某些HLA等位基因影响的疾病可能也会受到编码相应KIR分子的基因的影响。人类白细胞抗原和KIR基因的独立分离以及特定的人类白细胞抗原同种异型的KIR特异性增加了任何特定个体表达不存在配体的KIR分子的可能性。我们对一组银屑病关节炎患者进行了KIR基因分型，银屑病关节炎与人类白细胞抗原密切相关。这些数据表明，激活KIR2DS1和/或KIR2DS2基因的受试者易患银屑病关节炎，但只有当其同源抑制受体KIR2DL1和KIR2DL2/3的HLA配体缺失时才会发生银屑病关节炎。缺乏抑制KIR的配体可能通过激活受体而降低NK(和/或T)细胞激活的阈值，从而促进银屑病关节炎的发病。 我们最近已经完成了对来自两个宫颈癌队列(美国东部和哥斯达黎加)的500多人的分型，并正在对第三组进行分型。到目前为止的联合数据初步分析表明，抑制受体KIR3DL1和KIR2DL1在其HLA配体存在的情况下(分别为Bw4和Cw 2)具有保护性(3DL1+Bw4：OR=0.60，CI=0.41-0.88；2DL1+Cw 2：OR=0.67，CI=0.46-0.97)。当单独分析这些组时，也可以看到这些关联，尽管结果不那么显著，可能是由于样本量减少的结果。来自斯洛文尼亚的大约500例结直肠癌的KIR分型也已经开始，我们正在获取更多的对照样本。到目前为止的数据表明，激活受体KIR2DS1和KIR3DS1与疾病密切相关。我们已经发现了一个总体趋势，即激活KIR与传染病的有利结果有关，其中KIR3DS1的存在似乎在HIV疾病进展中具有保护作用，并可能在清除丙型肝炎病毒方面起到保护作用。相反，在自身免疫性疾病和癌症中，激活的KIRS往往与不利的结果有关。计划在下一财政年度对本文提到的每一种疾病进行全面、彻底的分析。

Natural killer (NK) cells are a unique group of lymphocytes involved in the surveillance and killing of foreign or infected cells through a mechanism involving recognition of HLA molecules by an extremely diverse set of receptors on the NK cell surface. The killer immunoglobulin-like receptor genes (KIRs) map to chromosome 19q13.4 along with other related genes. Some of these genes encode molecules that recognize HLA-C ligands, whereas others bind HLA-A and -B molecules. In contrast to cytotoxic T lymphocytes (CTL) recognition of peptide as presented by class I, NK cells destroy targets that lack expression of class I, and are inhibited by recognition of class I on the cell surface. NK cells play an important role in defense against virally infected cells and tumor cells that downregulate class I molecule expression, thereby avoiding recognition by CTL. For example, HIV-1 downregulates cell surface expression of HLA-A and -B molecules (but not -C) and one mechanism to explain rapid progression to AIDS in individuals with certain HLA types may involve alteration of NK cell activity (see Project number Z01 BC 10269-05 LGD). Evidence for downregulation of class I by human papilloma virus (HPV) has also been reported. Haplotypes of the KIR gene complex are extremely diverse, varying in the number and type of genes present, and some of the genes are polymorphic. We have developed a molecular typing technique to determine the presence or absence of each of the 15 KIR genes in order to study their potential effects on autoimmune (psoriatic arthritis [PsA], ankylosing spondylitis and multiple sclerosis), infectious diseases (those associated with HIV-1, hepatitis C virus, and hepatitis B virus), and cancer (colorectal and cervical). Initial studies have indicated the need to define diversity of KIR haplotypes in order to conduct rigorous disease association studies with this locus. Thus, in order to define KIR haplotypes and their frequencies we have typed 59 CEPH families for presence or absence of the KIR genes, representing nearly 1,400 KIR haplotypes (about 370 independent chromosomes and 1,000 meioses). Some KIR genes are found on almost all KIR haplotypes, so when one parent has two copies of a gene (one on each chromosome) and the other parent has one or two, all offspring are positive for the gene and it is not possible to determine whether one chromosome may be missing that gene locus. In some cases, it may be possible to resolve this problem by typing single nucleotide polymorphisms present in that gene. Thus, we have designed a sequence-based typing system for one of the common KIR genes, KIR2DL4, and an SSOP system for another common gene, KIR3DL1. KIR2DL4 allelic typing in the families is nearly complete and KIR3DL1 typing will be started shortly. It is clear from the data we have collected thus far that KIR haplotypes are extremely complex, and the most obvious mechanism for haplotypic variation appears to be unequal crossing over. However, the family data do not indicate a hotspot for recombination within the KIR gene complex. Ongoing typing and analyses of these haplotypes are underway. NK cell activity is partially controlled through interactions between KIR on NK cells and their respective HLA class I ligands. Given the functional relationship of these molecules, which are both encoded by highly polymorphic, unlinked regions of the genome, it is possible that diseases influenced by certain HLA alleles may also be affected by the genes encoding the corresponding KIR molecules. Independent segregation of HLA and KIR genes along with KIR specificity for particular HLA allotypes raises the possibility that any given individual may express KIR molecules for which no ligand is present. We have performed KIR genotyping in a cohort of individuals with psoriatic arthritis, a disease that is strongly associated with HLA. The data indicate that subjects with activating KIR2DS1 and/or KIR2DS2 genes are susceptible to developing psoriatic arthritis, but only when HLA ligands for their homologous inhibitory receptors, KIR2DL1 and KIR2DL2/3, are missing. Absence of ligands for inhibitory KIRs could potentially lower the threshold for NK (and/or T) cell activation mediated through activating receptors, thereby contributing to the pathogenesis of psoriatic arthritis. We have recently completed typing of more than 500 individuals from two cohorts of cervical cancer (Eastern US and Costa Rica) and are in the process of typing a third group. Preliminary analysis of the combined data thus far indicates that the inhibitory receptors KIR3DL1 and KIR2DL1 in the presence of their HLA ligands (Bw4 and Cw group 2 respectively) were protective (3DL1+Bw4: OR = 0.60, CI = 0.41-0.88; 2DL1+Cw group 2: OR = 0.67, CI = 0.46-0.97). These associations were also seen when the groups were analyzed separately, although the results were less significant, probably as a result of diminished sample size. KIR typing has also begun on a cohort of approximately 500 colorectal cancers from Slovenia and we are in the process of acquiring more control samples. The data thus far indicate that the activating receptors KIR2DS1 and KIR3DS1 show a significant association with disease. We have found a general trend for an association of activating KIRs with a favorable outcome in infectious diseases, where the presence of KIR3DS1 appears protective in HIV disease progression, and potentially in Hepatitis C virus clearance. Conversely, in autoimmune disease and cancer, the activating KIRs tend to be associated with an unfavorable outcome. A complete, thorough analysis of each of the diseases mentioned herein is planned for this next fiscal year.