Integrative approaches defining the ontogeny, maintenance, and immune response dynamics of marginal-zone B cells

项目摘要 战略定位为循环和免疫系统之间的守门人，脾边缘 区（MZ）B细胞形成抵抗血液传播病原体的前线。它们介导早期保护性 针对不同的T依赖性和T非依赖性抗原的反应，通过采用模糊 先天免疫和适应性免疫之间的界限。在人类中，MZ B细胞缺乏与IgM减少有关 滴度和对败血症的敏感性增加以及与包囊细菌感染相关的死亡率。在 此外，它们的功能和定位的损伤与几种自身免疫病理学有关。 尽管它们的重要性，MZ B细胞的个体发育和稳态的许多方面仍然不清楚。 MZ B细胞在其脾龛中的建立和维持由一组复杂的 调节细胞分裂、新骨髓（BM）衍生细胞流入、死亡等的规则 分化我们假设MZ B细胞动力学的规则随着年龄的增长而演变， 在免疫原性遭遇期间显著调制，导致其生态位大小的深刻变化 和克隆组成。在这里，我们提出了一种独特的综合方法，将数学和 定量绘制MZ B细胞的发育轨迹并解剖MZ B细胞的实验策略。 维持其数量和克隆多样性的机制，贯穿整个生命周期。 具体来说，我们将开发机械数学模型来描述来自验证的 实验系统，其中可以追踪MZ B细胞隔室内的组成性替换， 在健康小鼠体内长时间内。这种方法将使我们能够衡量营业额，揭示任何 MZ B细胞库内的异质性，并定义其发育轨迹。此外，我们将采用 并扩展这些确定性模型，以确定管理MZ B细胞小生境建立的规则， 早期生命，并将其制定为PDE系统，以量化细胞持续能力的动态转变， 作为它们进入房室后时间的函数。接下来，我们将开发动态建模策略 为了绘制免疫应答期间的B细胞分化途径，使用表达一种 抗原诱导型报告基因和Notch2中的B细胞特异性突变。最后，我们将采用 计算流水线研究活化B的单细胞免疫库和转录组学概况 细胞，并生成抗原特异性克隆的系统发育树，因为它们在免疫应答期间多样化。

Project Summary Strategically positioned as the gatekeepers between the circulation and the immune system, splenic marginal zone (MZ) B cells form a frontline of defense against blood-borne pathogens. They mediate early protective responses against diverse T-dependent and T-independent antigens, by employing strategies that blur the boundary between innate and adaptive immunity. In humans, MZ B cell deficiency is linked to reduced IgM titers and heightened susceptibility to sepsis and mortality related to encapsulated bacterial infections. In addition, impairment in their function and localization is associated with several autoimmune pathologies. Despite their importance, many aspects of the ontogeny and homeostasis of MZ B cells remain obscure. The establishment and maintenance of MZ B cells in their splenic niche are determined by a complex set of rules that regulate cell division, the influx of new bone marrow (BM) derived cells, death, and onward differentiation. We hypothesize that the rules governing MZ B cell dynamics evolve as we age, and are modulated significantly during immunogenic encounters, resulting in a profound variation in their niche size and clonal composition. Here, we propose a unique integrative approach that synthesizes mathematical and experimental strategies to quantitatively map the developmental trajectories of MZ B cells and dissect the mechanisms that maintain their numbers and clonal diversity, across the lifespan. Specifically, we will develop mechanistic mathematical models to describe the data derived from a validated experimental system in which one can track the constitutive replacement within the MZ B cell compartment, over long timescales in healthy mice. This approach will allow us to measure turnover, reveal any heterogeneity within the MZ B cell pool, and define their developmental trajectories. Further, we will adopt and extend these deterministic models to identify the rules governing the establishment of MZ B cell niche in early life and formulate them as PDE systems to quantify the dynamic transitions in cells’ ability to persist, as a function of time since their compartmental entry. Next, we will develop a dynamical modeling strategy to map B cell differentiation pathways during immune responses, using novel mouse strains expressing an antigen-inducible reporter gene and B cell-specific mutations in Notch2. Lastly, we will employ a computational pipeline to study the single-cell immune repertoire and transcriptomic profiles of activated B cells and to generate phylogenetic trees of antigen-specific clones as they diversify during immune responses.