The determinants of measures of immune function in a wild mammal.

动物产生免疫反应以保护自己免受感染。所有动物在其一生中都会受到感染：被感染是生活中正常的一部分。动物体内可感染病毒、细菌、原生动物（单细胞动物）和蠕虫，外部可感染蜱虫和螨虫。感染会对动物造成伤害，因为感染会破坏和破坏细胞和组织。动物为摆脱感染而做出的免疫反应需要大量的能量。因此，总的来说，被感染对动物来说是代价高昂的。除了感染外，野生动物在生活中还面临许多其他挑战。例如，它们必须寻找食物，而食物往往不是很丰富。此外，个体之间为了有限的食物而相互竞争。动物也会繁殖，这同样需要花费时间和精力。综上所述，野生动物的生活压力很大。这种压力的一个重要方面是动物可能没有足够的食物和能量来做出理想的免疫反应或完全投入繁殖等。因此，野生动物必须做出艰难的“决定”，即如何利用它们有限的资源来维持自己的生命，并将它们的基因传递下去。正因为如此，在一群动物中，个体的免疫反应会有所不同：有些会做出非常强烈的反应，有些会做出非常弱的反应。我们在一个试点项目中对此进行了调查，我们测量了野生小鼠的免疫反应，确实，我们发现不同个体的免疫反应差异很大。通过比较野生小鼠和实验室小鼠的免疫反应，我们还发现野生小鼠的免疫反应与实验室小鼠的免疫反应有很大的不同。我们现在想了解野生老鼠生活的哪些方面决定了它的免疫反应是很强还是很弱。对动物的实验室研究已经确定了许多可以影响免疫反应的因素：我们想要找出在野生小鼠身上，哪些因素起作用，以及影响程度有多大。影响免疫功能的因素包括性别（和性激素）、遗传、季节、年龄和身体状况。例如，男性荷尔蒙睾酮经常抑制免疫反应；喂食低蛋白质或低热量食物的动物通常会产生更弱或更慢的免疫反应。在我们的试点项目工作中，我们研究了野生老鼠，小家鼠。我们特别选择了这个物种，因为它也是实验室老鼠。人们对实验室小鼠的免疫学有了非常详细的了解，有很多工具和试剂可用于测量它们的免疫反应。这意味着我们可以很好地测量野生老鼠的免疫反应，比我们对几乎任何其他野生动物的免疫反应都要好得多。在我们提议的工作中，我们将对野生小鼠进行大规模调查，我们将测量它们的免疫功能以及它们生物学的许多其他方面，包括性别、遗传学、大小、体重、体脂百分比、瘦素（“脂肪”激素）浓度、性激素浓度等。然后，我们将寻找这些不同因素和免疫反应之间的联系，从而告诉我们是什么决定了野生小鼠的免疫反应。这将是第一个对野生哺乳动物免疫功能进行全面研究的研究。因此，这一结果将首次使我们了解野生动物免疫反应的主要控制因素。这项工作将有助于了解其他野生哺乳动物和动物的免疫功能。这一点非常重要，因为免疫功能及其在个体之间的差异对于影响野生种群中感染和疾病的流行非常重要。

Animals make immune responses to protect themselves from infections. All animals have infections during their life: being infected is a normal part of life. Animals can be infected internally with viruses, bacteria, protozoa (single-celled animals) and worms and externally with ticks and mites.Being infected causes harm to an animal because the infections damage and destroy cells and tissue. The immune responses that animals make to get rid of infections require a lot of energy. Therefore, overall, being infected is costly to an animal.Wild animals have many other challenges in their lives, apart from infections. For example, they have to search for food, which might often not be very abundant. Further, individuals compete with each other for limited amounts of food. Animals also reproduce which is, again, costly in time and energy. Putting this all together means that wild animals live stressful lives. One important aspect of this stress is that animals may not have enough food and energy to make ideal immune responses or to fully invest in reproduction etc. Therefore, wild animals have to make difficult 'decisions' about how to use their limited resources to keep themselves alive and to pass on their genes.Because of this, within a group of animals, individuals will vary in how good their immune responses are: some will make very strong responses, others very weak responses. We investigated this in a pilot project where we measured the immune responses of wild mice and, indeed, we found that different individuals vary a lot in the immune responses that they make. By comparing the immune responses of wild and laboratory mice we also found that the immune responses of wild mice are quite different to those of their laboratory cousins.We now want to understand what aspects of a wild mouse's life determines whether it makes a very strong immune response or a very weak immune response. Laboratory studies of animals have identified lots of things that can affect immune response: we want to find out which of these matter, and how much, in wild mice. Some factors that affect immune function are sex (and sex hormones), genetics, season, age and body condition. For example the male hormone testosterone often suppresses immune responses; animals fed low-protein or low-calorie diets often make weaker or slower immune responses. In our pilot project work we studied wild mice, Mus musculus. We particularly chose this species because this is also the laboratory mouse. There is a very detailed understanding of the immunology of laboratory mice and very many tools and reagents are available to measure their immune responses. This means that we could make very good measures of immune responses of wild mice, far better than we could for almost any other wild animal.In the work that we are proposing we will undertake a large survey of wild mice in which we will measure their immune function together with many other aspects of their biology including sex, genetics, size, weight, percent body fat, leptin (the 'fat' hormone) concentration, sex hormone concentrations etc. We will then look for associations between these different factors and immune responses, which will therefore tell us what determines the immune responses of mice in the wild. This will be the first study that will undertake a comprehensive study of immune function in wild mammals. The results will therefore, for the first time, allow us to understand the main controls of the immune responses of wild animals. This work will be relevant to understanding the immune function of other wild mammals and animals. This is important, not least, because immune function and its variation between individuals is important in affecting epidemics of infection and disease in wild populations.