Elucidating the local site and cell types involved in antigen uptake, processing and presentation in the chicken

成年生物体的血液和组织由多种细胞组成，包括携带氧气的红细胞和对抗疾病的免疫细胞。免疫细胞对病毒或微生物的感染作出反应，并启动细胞和分子防御机制，称为“免疫反应”。如果我们想要开发疾病控制措施，如疫苗接种，了解免疫系统如何保护身体免受疾病的侵害是至关重要的。大多数关于免疫反应的研究都是在人类和动物模型（如小鼠）中进行的。然而，了解农场动物的免疫系统是如何工作的是非常重要的。一个关键的例子就是鸡：鸡是地球上最受欢迎的食用动物，每年有超过500亿只鸡被孵化和饲养。在经济成本和动物福利方面，疾病控制是鸡肉生产的主要挑战。另一个因素是，一些禽类疾病，如禽流感，可能感染人类，因此对人类健康构成重大挑战。在食品安全、公众健康和消费者安全方面保护家禽业是至关重要的，不仅在英国，而且在全世界。增加我们对鸡的免疫系统和对疾病的免疫反应的理解的一个复杂因素是，鸡的免疫系统与哺乳动物的免疫系统非常不同。哺乳动物的一些专门用于免疫功能的器官，如淋巴结，在鸟类中是不存在的，而鸟类有自己的专门免疫器官，在哺乳动物中是不存在的。哺乳动物和鸟类之间的一些免疫细胞是相似的，但尚不清楚这些细胞是否具有相同的功能，还是对产生有效免疫反应有不同的要求。最重要的免疫细胞类型之一是单核吞噬细胞。这是一类具有许多不同功能的细胞，因此这些细胞有许多不同的子集。单核吞噬细胞的一个非常重要的功能是处理抗原物质并将其呈现给免疫系统的其他细胞，然后这些细胞可以做出适当的反应。从这个意义上说，它们将潜在病原体的性质信息传递给免疫系统的其余部分。关于在鸟类中捕获、加工和呈递抗原的细胞类型的信息很少。我们需要获得更多关于这些过程的信息，我们已经开发了一种新的工具来研究这些单核吞噬细胞，通过制造在单核吞噬细胞中表达荧光蛋白的转基因鸡（称为“MacReporter”鸡）。在我们对转基因鸟类的初步表征中，我们发现不仅可以识别所有的单核吞噬细胞，而且我们还可以识别整个免疫特异性组织。这特别有趣，因为这意味着我们可以用这些转基因鸡来描述这些免疫组织的结构，以及专门分析单核吞噬细胞。本研究计划的主要目标是使用MacReporter鸡来(1)识别鸡脾脏、呼吸道和胃肠道中参与抗原摄取和加工的细胞和组织；(2)对鸡脾抗原提呈细胞进行鉴定和功能表征；(3)确定哪些基因在不同类别的单核吞噬细胞中特异性表达，进一步定义和了解其功能。从长期来看，这些知识将为开发更好的疫苗提供信息，以预防鸡的疾病，目的是提高生产鸡的生产成本、生物安全和福利。

The blood and tissues of an adult organism consist of a number of cell types, including the red blood cells that carry oxygen and immune cells that fight disease. Immune cells respond to infection by viruses or microbes and initiate cellular and molecular defence mechanisms, known as an "immune response". An understanding of how the immune system defends the body against diseases is critically important if we want to develop disease control measures, such as vaccination. Most research on the immune response has been carried out on humans and in animal models such as mice. However, it is very important that we understand how the immune system of farm animals works. A key example of this is the chicken: the chicken is the most popular food animal on the planet, with over 50 billion being hatched and raised each year. Control of diseases is a major challenge in chicken production in terms of economic cost and animal welfare. An additional factor is that some bird diseases, such as bird flu, can potentially infect humans and are therefore a major challenge to human health. Protecting the poultry industry in terms of food security, public health and consumer safety is of paramount importance, not only in the UK, but worldwide. One complicating factor in increasing our understanding of the chicken's immune system and immune response to disease is that the bird's immune system is quite different to that of mammals. Some of the organs specialised for immune function in mammals, such as lymph nodes, are not present in birds, whereas birds have their own specialised immune organs that are not present in mammals. Some immune cells are similar between mammals and birds, but it is not known if these share the same functions or have different requirements for generation of an effective immune response. One of the most important types of immune cells are mononuclear phagocytes. These are a class of cells with many different functions and consequently there are many different subsets of these cells. One very important function of mononuclear phagocytes is to process antigen material and present it to other cells of the immune system, which can then respond appropriately. In this sense they communicate information on the nature of a potential pathogen to the rest of the immune system. There is very little information about what cell type(s) capture, process and present antigen in birds. We need to gain more information on these processes and we have developed a new tool for studying these mononuclear phagocytes by making transgenic chickens (called the "MacReporter" chicken) that express fluorescent proteins in mononuclear phagocytes. During our initial characterisation of the transgenic birds we found that not only could all mononuclear phagocytes be identified, but we could also identify entire immune-specific tissues. This is particularly interesting as this means that we can use these transgenic chickens to describe the structure of these immune tissues as well as analyse mononuclear phagocytes specifically. The main objectives of this research proposal are to use the MacReporter chicken to (1) identify cells and tissues involved in antigen uptake and processing in the chicken spleen, respiratory and gastrointestinal tracts; (2) identify and functionally characterise chicken splenic antigen presenting cells; (3) determine which genes are specifically expressed in the different classes of mononuclear phagocytes to further define and understand their function. In the longer term this knowledge will inform the development of better vaccines to prevent disease in chickens with the aim of improving production costs, biosecurity and welfare of production chickens.