Dynamic regulation of B cell recruitment in T-dependent humoral immune response

描述(由申请人提供)：T依赖体液免疫反应中B细胞募集的动态调节。(同源B-Th细胞相互作用、双光子成像、病毒逃逸突变体)在本项目中，我们将研究T依赖体液(抗体)免疫反应(TIR)的调节，以了解如何利用它来促进对健康、慢性病患者或免疫受损个体的有效体液保护，使其免受感染。为了产生长期、高亲和力的体液反应，罕见的抗原特异性B细胞必须获得外来抗原，然后接受同源Th细胞的帮助。虽然促进B-Th细胞相互作用和长期体液免疫的信号和转录因子已经得到了广泛的研究，但对于B细胞在体内募集到ThIR的重要分子机制仍然知之甚少。当抗原或T细胞的可获得性有限时，发现新的方法来优化B细胞和Th细胞之间初始同源相互作用的速度和效率对于诱导TIR至关重要。此外，在大流行感染迅速传播的情况下，疫苗预防也很重要。因此，这项应用的目的是确定哪些因素调节B细胞向ThIR的募集，以及当抗原或T细胞的帮助有限时它们的命运。我们的中心假设是，B细胞在THIR中的募集取决于(1)抗原对B细胞的可及性，以及(2)调节B细胞对T细胞帮助的反应性，(3)促进B-T细胞相遇，以及(4)如果没有获得T细胞帮助，决定B细胞的命运。我们在体内的初步数据表明，B细胞一次瞬时的抗原获取可能足以启动B细胞，帮助T细胞并参与生发中心和B细胞的记忆反应。然而，哪些分子因素调节B细胞能够获得T细胞帮助的时间和B细胞在体内的分化命运尚不清楚；也不知道罕见的激活的B细胞和Th细胞之间的相互作用是由相互吸引的分子信号促进的，还是稳定同源相互作用的分子线索。此外，在持续的病毒感染期间，体液免疫系统是否能够识别有限数量的病毒逃逸突变尚不清楚。我们将使用转基因淋巴细胞和模型抗原以及自然小鼠病毒感染模型-小鼠诺如病毒、双光子活体成像和数据定量分析来解决这些问题，并将表征控制THIR的新机制。这些结果预计将产生重要的积极影响，因为除了在总体上推进适应性免疫领域外，它们还可能导致改进现有的疫苗接种战略，并提出新的方法来增强免疫系统，以迅速抗击持续感染。

DESCRIPTION (provided by applicant): Dynamic regulation of B cell recruitment in T-dependent humoral immune response. (cognate B-Th cells interactions, 2-photon imaging, viral escape mutants) Project summary In this project we will study the regulation of T-dependent humoral (antibody) immune response (THIR) to learn how it can be manipulated to promote efficient humoral protection of healthy, as well as chronically sick or immunocompromised, individuals against infections. For generation of long-term, high-affinity humoral response, rare antigen-specific B cells have to acquire foreign antigen and then receive help from cognate Th cells. While the signaling and transcription factors promoting B - Th cell interactions and long-term humoral immunity have been extensively investigated, the molecular mechanisms important for recruitment of B cells into THIR in vivo are still poorly understood. Discovering novel ways to optimize the speed and efficiency of initial cognate interactions between B and Th cells is critical for induction of THIR when antigen or T cell help availability is limited. In addtion, it is important for vaccine prophylaxis in the case of rapidly spreading pandemic infections. Therefore, the objective of this application is to determine which factors regulate recruitment of B cells into THIR, and their fate when Ag or T cell help availability is limited. Our central hypothesis is that recruitment of B cells into THIR depends on (i) accessibility of Ag to B cells, and on molecular factors that (ii) regulate B cell responsiveness to T cell help, (iii) promote B-T cell encounters, and (iv) determine B cell fate if T cell help is not acquired. Our preliminary in vivo data suggests that single transient Ag acquisition by B cells may be sufficient to prime B cells for T cell help and participate in the germinal center and B cell memory responses. However, which molecular factors regulate the time that B cells are capable of acquiring T cell help and B cell differentiation fate in vivo is not known; and whether interactions between rare activated B and Th cells are promoted by molecular cues that attract them to each other or stabilize cognate interactions have not been addressed. In addition, whether limiting amounts of viral escape mutants could be recognized by the humoral immune system during ongoing viral infection is unclear. We will address these questions using transgenic lymphocytes and model antigens, as well as the natural mouse viral infection model - Murine Norovirus, two- photon intravital imaging and quantitative analysis of the data, and will characterize novel mechanisms that control THIR. Such results are expected to have an important positive impact because in addition to advancing the field of adaptive immunity in general, they could lead to improvements in existing vaccination strategies and suggest new ways to boost the immune system to rapidly fight ongoing infections.