Development and significance of the plasma cell niche in the human infant thymus

项目摘要 我们的初步研究揭示了人类B细胞亚群的动态演变作为年龄的函数。 胸腺在出生时存在并显示幼稚B细胞表型的最初的髓B细胞是 逐渐被抗原经验丰富、分泌抗体、类别转换的浆细胞所取代， 血管周围间隙（PVS）。出生后几个月，PVS中开始出现浆细胞 这与早期暴露于常见地方性病毒和疫苗抗原相一致。我们建议 后一个亚群由先前的免疫产生，并构成记忆B细胞的重要库， 浆细胞因此，成熟的胸腺代表了一个未被认识到的B细胞记忆的小生境 在骨髓旁边我们还假设，胸腺驻留浆细胞显着有助于 通过其组成性抗体分泌能力的体液免疫。我们建议的研究将使用 从0-2岁的捐赠者中获得的大量人体标本，以进一步表征这一生态位 在其早期发展中。使用模型抗原免疫的小鼠，我们将研究其机制 由此PC在胸腺中积累并有助于总体血清免疫。 目标1.目的：研究人婴儿胸腺浆细胞生态位的特征。我们会研究 在约250例来自0-2岁供体的人胸腺标本中，胸腺PC生态位发育的动力学。 使用免疫化学，流式细胞术，基因表达谱和下一代测序- 基于IGVH库分析，我们将表征IGVH的结构、分子特征和克隆特性。 人婴儿胸腺PC的组成。正常人脾脏和骨髓中PC亚群的比较 相同的供体将揭示胸腺PC是否具有独特的特征。 目标2.确定人类婴儿胸腺浆细胞的反应性特征。在目标2中，我们将 评估胸腺PC对人类婴儿所针对的广泛抗原反应的频率， 暴露了其中包括疫苗接种病毒和细菌抗原、常见食物抗原以及ABO血液 群抗原胸腺中抗原特异性B细胞与 将检查对相同抗原具有特异性的血清IgG。 目标3.探讨胸腺PC的来源及其在血清免疫中的作用。免疫的小鼠 用模型T细胞依赖性和T细胞非依赖性抗原，将用于验证胸腺PC起源于 来自外周免疫反应。然后，我们将使用一系列遗传缺陷小鼠品系， 研究特异性趋化因子和趋化因子受体以及生存因子在 胸腺PC的迁移和维持。最后，我们将评估抗原经历的胸腺细胞的能力， PC在过继转移或移植胸腺片段时赋予体液免疫 受体动物的肾包膜。

Project Summary Our preliminary studies revealed the dynamic evolution of B cell subsets as a function of age in the human thymus. An initial contingent of medullary B cells present at birth and displaying a phenotype of naive B cells is progressively replaced by antigen-experienced, antibody-secreting, class-switched plasma cells confined within the perivascular space (PVS). Plasma cells start to appear in the PVS a few months after birth at a time that is consistent with early exposure to common endemic viruses and vaccination antigens. We propose that this latter subset results from previous immunization and constitute an important pool of memory B cells and plasma cells. The maturing thymus would therefore represent an unrecognized niche for B cell memory alongside the bone marrow. We also hypothesize that thymic resident plasma cells significantly contribute to the humoral immunity through their constitutive antibody-secreting capacity. Our proposed studies will use a large collection of human specimens obtained from donors aged 0-2 years to further characterize this niche during its early development. Using mice immunized with model antigens, we will then investigate mechanisms whereby PC accumulate in the thymus and contribute to the overall serum immunity. Aim 1. To characterize the thymic plasma cell niche in the human infant thymus. We will examine the kinetics of development of the thymic PC niche in ~250 human thymus specimens from donors aged 0-2 years. Using immunochemistry, multicolor flow cytometry, gene expression profiling and next generation sequencing- based IGVH repertoire analysis, we will characterize the architecture, molecular signature and clonal composition of thymic PC in human infants. A comparison with PC subsets in the spleen and bone marrow of the same donors will reveal whether thymic PC have unique features. Aim 2. To determine the reactivity profile of thymic plasma cells in human infants. In aim 2, we will assess the frequency of thymic PC reactive to a broad range of antigens towards which human infants are exposed. These include vaccination viral and bacterial antigens, common food antigens as well as ABO blood group antigens. The possible correlation between antigen-specific B cells in the thymus and the presence of serum IgG specific to the same antigens will be examined. Aim 3. To verify the origin of thymic PC and evaluate their role in serological immunity. Mice immunized with model T cell-dependent and T cell-independent antigens, will be used to verified that thymic PC originate from peripheral immune responses. We will then use a series of genetically-deficient mouse strains to investigate the implication of specific chemokines and chemokine receptors as well as survival factors in the migration and maintenance of thymic PC. Lastly, we will evaluate the capacity of antigen-experienced thymic PC to confer humoral immunity upon adoptive transfer to or transplantation of thymus fragments under the renal capsule of recipient animals.