Dissecting the functional impact of natural killer cell receptor variation in cattle.

对生物体健康的挑战由免疫系统来应对。这些挑战可能来自外部来源，如细菌、病毒或过敏原，也可能来自内部来源，如肿瘤。应对所有这些挑战是一项艰巨的任务，并导致高度复杂的免疫系统。病原入侵者不断变化，试图避免免疫检测。这反过来又驱动免疫系统，促进宿主和病原体的变化和适应的重复循环。在多种免疫细胞上表达的多种受体是宿主适应的重要组成部分。哺乳动物基因组中有很大一部分（约5%）与免疫系统有关，特别是那些形成基因簇和家族的免疫受体。在这些家族中，突变和种系重组为新基因和旧基因的新变体创造了来源。事实上，免疫相关基因比哺乳动物基因组中任何其他类型的基因都更加多样化。自然杀伤细胞（NK）上表达了一组不同的可变和多样化的受体。NK细胞是对病原体的第一反应者之一。NK反应的大小随后指导免疫系统的其余部分如何反应。NK细胞由一些最多样化的免疫受体控制，在抗病毒免疫中尤为重要。在哺乳动物中，牛具有迄今为止发现的最多样化的NK细胞受体系统。随着这一系统进化到对抗感染，有必要在牛身上检查这一系统，以了解这些经济上至关重要的动物如何对抗感染。这一知识将使应用研究能够改进疫苗和培育抗病品种。本研究将利用牛基因组信息和高通量DNA测序技术，全面表征6头荷斯坦-弗里沙奶牛的NK细胞受体基因家族。这是一个重要的经济品种在英国和世界各地。通过比较该品种内的几只动物，我们可以确定NK细胞受体多样性的程度。利用这些受体的知识，我们将确定它们与感染细胞相互作用以控制NK细胞功能的分子。这将决定具有不同NK细胞受体的动物是否可能对感染做出不同的反应。最后，我们将感染已知能激活NK细胞的特定牛细胞，这些细胞反过来又被NK细胞激活。这些牛将感染一种已知的经济上重要的牛病原体，牛疱疹病毒-1。然后，我们将这些感染细胞与表达不同NK细胞受体基因的NK细胞孵育。通过测量这些NK细胞的功能和受感染细胞的反应，就有可能确定NK细胞的变异是否会引起不同的免疫反应。了解NK细胞如何根据受体对病毒感染作出反应是必要的。这项基础研究将允许未来检查个体动物对个体病原体和疫苗接种的反应如何变化。这将创造机会，通过基因组选择育种策略增加有益基因的频率，并更准确地衡量疫苗如何有效地保护动物免受病原体的攻击。

Challenges to the health of an organism are met by the immune system. These challenges can arise from external sources, such as bacteria, viruses, or allergens as well as internal sources such as tumours. Meeting all these challenges is a difficult task and has resulted in a highly complex immune system. Pathogenic invaders are constantly changing in an attempt to avoid immune detection. This in turn drives the immune system, fostering a repetitive cycle of change and adaptation for both the host and pathogen. Diverse receptors expressed on a variety of immune cells are an essential part of this host adaptation. A significant proportion (~5 %) of mammalian genomes is dedicated to the immune system, particularly those immune receptors which form gene clusters and families. Within these families mutation and germ-line recombination creates a source for new genes and new variants of old genes. In fact, immune related genes have diversified more than any other type in mammalian genomes. A distinct set of variable and diverse receptors are expressed on natural killer (NK) cells. NK cells are one of the first responders to pathogens. The magnitude of the NK response subsequently directs how the rest of the immune system responds. NK cells are controlled by some of the most diverse immune receptors identified and are especially important in antiviral immunity. Amongst mammals, cattle have the most diverse NK cell receptor system so far identified. As this system evolved to combat infection, it is essential to examine this system in cattle to understand how these economically crucial animals fight infection. This knowledge will enable applied studies to improve vaccines and breed for disease resistance. This proposal will use information from the cattle genome and high-throughput DNA sequencing technology to completely characterise the NK cell receptor gene families in six Holstein-Friesian dairy cattle. This is an economically important breed in the UK and worldwide. By comparing several animals within this breed we can determine the extent of NK cell receptor diversity. Using knowledge of these receptors, we will determine the molecules that they interact with on infected cells to control NK cell function. This will determine if animals that have dissimilar NK cell receptors are likely to respond differently to infection. Finally, we will infect particular cattle cells that are known to activate NK cells and in turn become activated by NK cells. These will be infected with a known economically important cattle pathogen, bovine herpes virus-1. We will then incubate these infected cells with NK cells that express different NK cell receptor genes. By measuring how these NK cells function and how the infected cells respond, it will be possible to determine if NK cell variation causes different immune responses.Knowledge of how NK cells respond to virus infection depending on their receptors is essential. This fundamental research will allow future examination of how individual animals vary in their response to individual pathogens and vaccination. This will create opportunities to increase the frequency of beneficial genes through genomic selection breeding strategies and more accurately measure how effective vaccines protect animals from pathogen challenge.