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细胞亚群随年龄的动态演变 胸腺。出生时存在的最初的髓B细胞，表现为幼稚的B细胞表型 逐渐被抗原经验丰富、抗体分泌、类别转换的受限浆细胞所取代 在血管周围间隙(PVS)内。浆细胞在出生后几个月开始出现在PVS中，一次出现 这与早期接触常见的地方性病毒和疫苗接种抗原是一致的。我们建议 后一个子集是先前免疫的结果，并构成一个重要的记忆B细胞池和 浆细胞。因此，成熟的胸腺将代表着B细胞记忆的一个未知的利基 和骨髓一起。我们还假设胸腺驻留浆细胞对 体液免疫是通过其固有的抗体分泌能力实现的。我们建议的研究将使用 从0-2岁的捐赠者那里获得大量人类标本，以进一步表征这一利基环境 在它的早期发展过程中。用模型抗原免疫的小鼠，然后我们将研究机制 PC在胸腺中蓄积，对整体血清免疫有贡献。 目的1.研究婴儿胸腺中胸腺浆细胞的生态位。我们将研究 ~250例0~2岁人胸腺标本胸腺PC生态位发育的动力学研究 利用免疫化学、多色流式细胞术、基因表达谱和下一代测序- 基于IGVH谱系分析，我们将对其结构、分子特征和克隆进行表征 人类婴儿胸腺PC的组成。小鼠脾和骨髓中PC亚群的比较 同样的捐赠者将揭示胸腺PC是否具有独特的功能。 目的2.测定婴儿胸腺浆细胞的反应性分布。在目标2中，我们将 评估胸腺PC对人类婴儿对多种抗原的反应频率 暴露了。这些包括接种病毒和细菌抗原、常见食物抗原以及ABO血液。 组抗原。胸腺中抗原特异性B细胞与AFP存在的可能相关性 将检测针对相同抗原的血清免疫球蛋白。 目的3.验证胸腺PC的来源，评价其在血清免疫中的作用。免疫的小鼠 与模型T细胞依赖和T细胞非依赖抗原，将被用来验证胸腺PC起源 来自外周免疫反应。然后我们将使用一系列基因缺陷的小鼠品系来 探讨特异性趋化因子、趋化因子受体及生存因子在急性髓系白血病中的意义 胸腺PC的迁移和维护。最后，我们将评估抗原经历的胸腺的能力。 PC在胸腺片段过继转移或移植时授予体液免疫 受体动物的肾被膜。

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.