Discovering the Role of Commensal Microbes on Primary B Lymphocyte Development

描述(申请人提供)：现代免疫学的一个基本目标是了解有助于共生微生物和宿主免疫系统之间的动态平衡的因素。虽然已经做了很多工作来了解共生体在塑造T细胞反应中的作用，但在理解共生体如何影响B淋巴细胞发育和相关抗体多样化方面仍存在很大差距。这一差距的持续存在是一个重要的问题，因为在填补之前，我们对体液免疫适应性以及对过敏和炎症性疾病易感性的调节原则的理解将仍然不完整。这项建议的总体目标是确定共生微生物如何影响初级B细胞发育和免疫前免疫球蛋白(Ig)的多样化。根据申请人最近的发现，中心假设是共生微生物通过宿主感官工具提供输入，调节宿主肠道粘膜中的早期B细胞发育活动，从而使管腔抗原具有影响局部初级Ig谱系的能力。这与其他几个物种，如兔子和绵羊，在出生后早期利用肠道作为初级免疫球蛋白多样化的重要部位的观察是一致的。提出的研究的基本原理是，一旦完成，该领域将在垂直方向上更好地理解共生体在免疫稳态中的作用，并将为进一步探索可有针对性的可改变的环境因素打开大门，从而产生新的创新方法来影响与抗体生产相关的各种健康问题。利用新技术和现有技术，这项提案的三个目标将建立在申请人最近的工作基础上。随着体外共培养的部署以及体内标记方法的建立，Aim 1将测试共生体影响肠道驻留和骨髓支持系统以刺激早期B系细胞发育的概念，并有望确定使早期B系细胞存活并对微生物输入做出反应的肠道驻留支持机制。随着无菌和生菌设施的使用，目标2将确定微生物组成对形成主要免疫球蛋白谱系的特定影响的程度。借助复杂的转基因小鼠模型和强大的成像技术，Aim 3将评估肠腔抗原进入幼鼠肠道固有层并与新鲜产生的细胞结合的Ig相互作用的程度。这项拟议的研究具有重要的意义，因为以下三个原因-第一，它有望提供更完整的宿主一般原理的图景：微生物在免疫调节中的相互作用；第二，它将是确定早期可改变的环境暴露对初级Ig谱系的影响程度的第一步；第三，它提供了一个必要的组成部分，为检验未来关于特定共生微生物生态对病原体、过敏原和疫苗的下游抗体反应的影响的假说提供了一个必要的组成部分。

DESCRIPTION (provided by applicant): A fundamental goal in modern immunology is to understand the factors that contribute to the homeostatic balance between commensal microbes and the host immune system. Although a great deal has been done to understand the role of commensals in shaping T cell responses, a large gap remains in understanding how commensals impact B lymphocyte development and associated antibody diversification. Continued existence of this gap is an important problem because until filled, our understanding of regulatory principles underlying humoral immune fitness as well as vulnerability to allergic and inflammatory diseases will remain incomplete. The overall objective of this proposal is to determine how commensal microbes affect primary B cell development and pre-immune immunoglobulin (Ig) diversification. Based on recent findings from the applicant, the central hypothesis is that commensal microbes provide inputs through host sensory instruments to regulate early B cell developmental activities in the host gut mucosa, thus empowering luminal antigens with the capacity to influence the primary Ig repertoire locally. This is consistent with observations that several other species, such as rabbits and sheep, utilize the intestine as a significant site for primary Ig diversification early in post-natal life. The rationale for the proosed research is that, once accomplished, the field will move vertically towards a greater understanding of the role of commensals in immune homeostasis and will open the door to further exploration of modifiable environmental factors that could be targeted, resulting in new and innovative approaches to influence a variety of health issues relevant to antibody production. Using both new as well as established technologies, this proposal's three aims will build upon the applicant's recent work. With the deployment of ex vivo co-culture as well as established in vivo labeling methods, aim 1 will test the notion that commensals influence both gut-resident as well as bone marrow support systems to stimulate early B lineage cell development and is expected to identify the gut-resident support mechanisms enabling early B lineage cells to survive and respond to microbial input. With the use of germ-free and gnotobiotic facilities, aim 2 will determine the extent to which microbe composition has specific effects to shape the primary Ig repertoire. With sophisticated genetically modified mouse models as well as powerful imaging technologies, aim 3 will evaluate the degree to which luminal antigens gain access to the intestinal lamina propria and interact with freshly-produced, cell-bound Ig in young mice. The proposed research is significant for the following three reasons - first, it promises to provide a more complete picture of the general principles of host:microbe interactions in immune regulation; second, it will be a first step to identify the extent to which primary Ig repertoires can be influenced by modifiable environmental exposures early in life; and third, it provides an essential component to establish a platform for testing future hypotheses regarding the effect of specific commensal microbe ecologies on downstream antibody responses to pathogens, allergens and vaccines.