Cellular dynamics in germinal centers during vaccination

描述（由申请人提供）：产生适当同型的高亲和力抗体对于宿主防御细胞外病原体和大多数疫苗的成功至关重要。生发中心既是亲和成熟的场所，也是T细胞依赖类转换的场所。在之前的资助期内，我们进行了一系列活体显微镜研究，揭示了生发中心功能的新方面。研究表明：1)生发中心是动态开放结构，生发中心B细胞在明暗区之间迁移；2)明暗区细胞表现出相似的形状、大小和行为；3)幼稚B细胞可以通过生发中心迁移；4)生发中心可随时被亲和力较高的B细胞侵袭；5)血浆原细胞在淋巴结中表现出一种新的从卵泡到髓索的迁移模式——一种“随机冲刺”，这是在没有特定趋化提示的情况下在组织中各细胞间移动的最佳方式；6)生发中心区间迁移的循环再入模型是正确的，亮区向暗区迁移是由T细胞帮助控制的。在本提案中，我们提出了两个新的目标，重点关注T细胞在控制早期选择事件中的作用以及滤泡辅助性T细胞如何与生发中心B细胞通信。我们假设：1)B细胞之间基于亲和力的竞争发生在生发中心反应之前；2) T细胞抑制自身反应性B细胞的出现，3)T细胞通过TCR阳性微泡与B细胞交流，TCR阳性微泡通过动态细胞-细胞连接或激酶转移。我们将通过两个特定目的来验证这些假设：1)表征生发中心亲和竞争和T细胞介导的B细胞耐受调节；2)在体外和体内研究微囊泡在T细胞与GC - B细胞通讯中的作用。我们预计这些研究将解决这些假设的有效性，并对未来疫苗的设计方式产生影响。

DESCRIPTION (provided by applicant): Generation of high affinity antibodies of the appropriate isotype is essential for host defense against extracellular pathogens and for the success of most vaccines. Germinal centers are the sites of both affinity maturation and T cell dependent class switching take. In the previous funding period we performed a series of intravital microscopy studies that revealed novel aspects of germinal center function. We demonstrated that 1) germinal centers are dynamic open structures and that germinal centers B cells migrate between light and dark zones; 2) light and dark zone cells display similar shape size and behavior; 3) naive B cells can migrate through germinal centers; 4) germinal centers can be invaded at any time by higher affinity B cells; 5) plasma blasts display a novel mode of migration in lymph nodes in moving from the follicle to the medullulary cords- a "random sprint" which is the best way to travel between compartments in a tissue without specific chemotactic cues; 6) that the cyclic reentry model for interzonal migration in germinal centers is correct and that light zone to dark zone migration is controlled by T cell help. In this proposal we propose two new Aims focusing on the role of T cells in controlling early selection events and how follicular helper T cells communicate with germinal center B cells. We hypothesize that 1) affinity based competition between B cells takes place prior to the germinal center reaction; 2) that T cells suppress the emergence of autoreactive B cells and 3) that T cells communicate with B cells through TCR positive microvesicles that are transferred through a dynamic cell-cell junction, or kinapse. We will test these hypotheses through 2 specific Aims: 1) to characterize germinal center affinity competition and T cell mediated regulation of B cell tolerance in the germinal center; and 2) to determine the role of microvesicles in T cell communication with GC B cells in vitro and in vivo. We anticipate that these studies will address the validity of these hypotheses and have an impact on the way that vaccines are designed in the future. PUBLIC HEALTH RELEVANCE: Vaccination is one of the most significant contributions of modern immunology to public health. However, some pathogens including HIV have been very difficult to vaccinate against. The proposed studies will provide new insights into mechanisms operating in germinal centers including somatic mutation that are essential to developing novel vaccination strategies to overcome barriers to host protection.