Effects of neonatal microbial exposure on anti-polysaccharide B cell development

摘要 针对 T 独立多糖 (PS) 的先天样 B 细胞衍生的天然抗体 (NAb) 和 磷脂表位普遍存在于哺乳动物中，在防止病毒感染方面发挥着重要作用。 许多细菌病原体。然而，感染后针对 PS 抗原的强烈抗体反应或 新生儿缺乏免疫接种。我们之前表明，新生儿接触 PS 和磷脂 通过免疫或微生物群的自然定植产生抗原，影响克隆分布 抗原特异性先天样 B 细胞导致天然抗体 (Nab) 水平定量增加。这些 影响成人对感染的易感性以及对过敏原和自身抗原的免疫反应 具有相似的 B 细胞表位。尽管微生物群影响其他淋巴谱系的发育，但 在成人先天样 B 细胞和 NAb 库发育中的作用很大程度上尚未被探索。我们的 假设除了 B 细胞发育过程中发生的详细描述的选择过程外， 自体抗原和外源共生衍生表位在新生儿期结合的可及性 发展以塑造自然剧目。这些拟议研究的目的是阐明机制 使用三种模型 B 细胞抗原对先天性 B 细胞库进行外源抗原定向开发 代表相关致病菌和共生生物体表位的特异性，具有一系列自动谱 抗原潜力：磷酸胆碱 (PC)、N-乙酰基-D-葡萄糖胺 (GlcNAc) 和葡聚糖 (DEX)。目标 1 这些研究将用特定的微生物群定植野生型无菌小鼠，以评估 外源抗原信号传导对克隆 B 细胞发育和 NAb 库形成的影响。骨髓 嵌合系统，由抗原特异性免疫球蛋白（Ig）重链转基因小鼠品系组成， 谱系追踪将能够评估 B 淋巴细胞上的内源性和外源性抗原信号传导 选择和受体编辑过程。在目标 2 中，我们将分析频率、细胞表面表型、 人类 B 细胞的子集和同种型分布以及免疫球蛋白基因的使用 抗原。检查从脐带血、扁桃体/腺样体和外周血 B 细胞中分离的 B 细胞 不同年龄的捐赠者将为抗原体验在先天性抗原形成中的作用提供新的见解。 例如个体内部和个体之间的 B 细胞库多样性。抗原特异性 Ig 基因将被克隆并 表达为重组抗体，以确定抗原驱动的成熟对这些功能的影响 人类抗体。总的来说，这些研究将确定微生物对小鼠 NAb 发育的影响， 确定人类 NAb 发育的发育动力学，并比较和对比 NAb 库 两个物种之间的发展。了解人类婴儿对感染和定植的反应 将推进我们开发有效的新生儿疫苗策略和介入疗法的长期目标 提供针对传染性病原体以及过敏性和自身免疫性疾病的保护。

ABSTRACT Innate-like B cell-derived natural antibodies (NAbs) against T-independent polysaccharide (PS) and phospholipid epitopes are universally present in mammals and serve important roles in the protection against many bacterial pathogens. However robust antibody responses against PS antigens following infection or immunization are absent in neonates. We previously showed that neonatal exposure to PS and phospholipid antigens by immunization or natural colonization with the microbiota, influences the clonal distribution of antigen-specific innate-like B cells leading to quantitative increases in natural antibody (Nab) levels. These effects impact adult susceptibility to infection, and immune-responsiveness to allergens and auto antigens bearing similar B cell epitopes. Although the microbiota impacts the development of other lymphoid lineages its role in the development of the adult innate-like B cell and NAb repertoires is largely unexplored. Our hypothesis is that in addition to the well-described selection processes that occur during B cell development, the accessibility to autologous antigens and exogenous commensal-derived epitopes combine during neonatal development to shape the natural repertoire. The goal of these proposed studies is to elucidate mechanisms of exogenous antigen-directed development of the innate-like B cell repertoire using three model B cell antigen- specificities that represent epitopes for relevant pathogenic and commensal organisms with a spectrum of auto antigenic potential: phosphorylcholine (PC), N-acetyl-D-glucosamine (GlcNAc), and dextran (DEX). In Aim 1 of these studies wild-type gnotobiotic mice will be colonized with defined microbiota to assess the contribution of exogenous antigen signaling on clonal B cell development and formation of the NAb repertoire. Bone marrow chimera systems, composed of antigen-specific immunoglobulin (Ig) heavy chain-transgenic mouse strains, and lineage tracking will enable assessment of endogenous and exogenous antigen signaling on B lymphocyte selection and receptor editing processes. In Aim 2 we will analyze the frequency, cell surface phenotype, subset and isotype distribution as well as immunoglobulin gene usage of human B cells specific for these antigens. Examination of B cells isolated from cord blood, tonsils/adenoids, and peripheral blood B cells of donors of different ages will provide novel insight into the role of antigen experience in the formation of innate- like B cell repertoire diversity within and across individuals. Antigen-specific Ig genes will be cloned and expressed as recombinant antibody to determine effects of antigen-driven maturation on functions of these human antibodies. Collectively, these studies will define the microbial influences on NAb development in mice, determine developmental kinetics of human NAb development, and compare and contrast the NAb repertoire development between both species. This insight into the human infant responses to infection and colonization will advance our long-term goal of developing effective neonatal vaccine strategies and interventional therapies that provide protection from infectious pathogens and allergic and autoimmune diseases.