Regulation of germinal center B cell fate choice by Hedgehog signaling

Hedgehog 信号传导调控生发中心 B 细胞命运选择

• 批准号: 10570972
• 负责人: ANN M HABERMAN
• 金额: $ 20.94万
• 依托单位: YALE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-02-11 至 2024-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10570972
• 关键词: Ablation; Address; Affinity; Antibody Formation; Antigen-Antibody Complex; Antigens; Apoptosis; B-Cell Antigen Receptor; B-Lymphocyte Subsets; B-Lymphocytes; Back; Cell Cycle; Cell Lineage; Cell division; Cells; Centroblast; Centrocyte; Chemicals; Clonal Expansion; Complement Receptor; Darkness; Data; Erinaceidae; Event; Family member; Fc Receptor; Flow Cytometry; Follicular Dendritic Cells; Gene Expression; Genes; Genetic Transcription; Hair follicle structure; Helper-Inducer T-Lymphocyte; Histologic; Humoral Immunities; Image; Immune response; Immunization; Immunoglobulin-Secreting Cells; Instruction; Light; Memory; Memory B-Lymphocyte; Molecular; Movement; Neighborhoods; Periodicity; Plasma Cells; Play; Population; Process; Production; Proliferating; Receptor Signaling; Regulation; Resistance; Rest; Role; SHH gene; Stromal Cells; Structure of germinal center of lymph node; T-Lymphocyte; Testing; Transition Elements; Vaccines; Variant; autocrine; cell behavior; cell type; epithelial stem cell; epithelial to mesenchymal transition; experimental study; in vivo; intestinal crypt; long term memory; migration; overexpression; pathogen; receptor; self renewing cell; self-renewal; smoothened signaling pathway; stem cell differentiation; stem cell niche; stemness

Project Summary Effective humoral immunity critically depends on the formation of germinal centers (GC) that generate high- affinity, long-lived memory and plasma cells. Within mature GCs, histologically distinct dark (DZ) and light zones (LZ) can be observed, the latter defined by the presence of a stromal cell type, follicular dendritic cells (FDCs). FDCs express high levels of complement and Fc receptors that retain immune complexed antigen. In addition to a depot of antigen, the LZ also harbors the majority of T follicular helper cells (Tfh). GC B cells undergo many rounds of cell division and profound shifts in gene expression during cycles of selective clonal expansion. The selection of LZ GC B cells with B cell receptors (BCR) of higher affinity involves antigen acquisition, BCR signaling and competition for Tfh cell contacts. After engagement and instruction by Tfh cells, LZ B cells undergo transcriptional rewiring that propels their movement to the DZ where they complete one or more cell divisions. Through a poorly understood process, DZ B cells eventually lose their propensity to remain within that zone and migrate back to the LZ as centrocytes. This iterative cyclic process ultimately results in the selective expansion of higher affinity BCR variants. In addition to their clonal self-renewal, GC B cells also give rise to long-term memory B cell and plasma cell lineages that exit the GC during maturation. The factors that regulate the cell fate choice of reactivated GC B cells are incompletely understood. Recent studies are consistent with the idea that stronger BCR signaling within the LZ promotes the plasma cell lineage while the formation of memory B cells predominates among GC B cells with BCRs of lower affinity for antigen, presumed to be the result of insufficient engagement of Tfh cells due to poor antigen acquisition and presentation. However, the role that FDC-derived factors might play in GC B cell fate choices have not been examined. The factors that regulate the cell fate choice of reactivated LZ B cells is poorly understood. We questioned whether stromal cell-derived factors influencing cell behavior in those niches could also play a role in GCs. We hypothesize that Hedgehog signaling plays a role in critical transitions during GC B cell re-activation that influence cell fate. We propose to define the Hedgehog dependent and independent events and their impact on GC B cell lineage divergence. These questions will be addressed through the inhibition or ablation of Hedgehog signaling and an examination of the effect on GC B cell self-renewal or the initiation of differentiation to alternative cell lineages within the GCs. Proposed experiments to assess the molecular impact of Hedgehog signaling include scRNAseq of GC B cells.

项目概要 有效的体液免疫主要取决于生发中心（GC）的形成，生发中心产生高 亲和力、长寿命记忆和浆细胞。在成熟的 GC 中，组织学上不同的暗色 (DZ) 和亮色 可以观察到区域（LZ），后者由基质细胞类型（滤泡树突状细胞）的存在来定义 （FDC）。 FDC 表达高水平的补体和 Fc 受体，保留免疫复合抗原。在 除了抗原库之外，LZ 还含有大部分滤泡辅助 T 细胞 (Tfh)。 GC B细胞 在选择性克隆周期中经历多轮细胞分裂和基因表达的深刻变化 扩张。具有更高亲和力的B细胞受体（BCR）的LZ GC B细胞的选择涉及抗原 采集、BCR 信号传导和 Tfh 细胞接触的竞争。经过 Tfh 细胞的参与和指导后， LZ B 细胞经历转录重连，推动它们运动到 DZ，在那里它们完成一项或多项任务 更多的细胞分裂。通过一个鲜为人知的过程，DZ B 细胞最终失去了保留的倾向 在该区域内并作为中心细胞迁移回 LZ。这个迭代循环过程最终导致 选择性扩增更高亲和力的 BCR 变体。除了克隆自我更新之外，GC B 细胞还提供 产生长期记忆 B 细胞和浆细胞谱系，并在成熟过程中退出 GC。那些因素 调节重新激活的 GC B 细胞的细胞命运选择的机制尚不完全清楚。最近的研究是 与 LZ 内更强的 BCR 信号传导促进浆细胞谱系的观点一致，而 据推测，记忆 B 细胞的形成在 GC B 细胞中占主导地位，其 BCR 对抗原的亲和力较低 这是由于抗原获取和呈递不良导致 Tfh 细胞参与不足的结果。 然而，FDC 衍生因子在 GC B 细胞命运选择中可能发挥的作用尚未得到研究。 对于调节重新激活的 LZ B 细胞的细胞命运选择的因素知之甚少。我们质疑 影响这些微环境中细胞行为的基质细胞衍生因子是否也能在 GC 中发挥作用。我们 假设 Hedgehog 信号在 GC B 细胞重新激活过程中的关键转变中发挥作用 影响细胞命运。我们建议定义刺猬相关事件和独立事件及其对 GC B 细胞谱系分歧。这些问题将通过抑制或消融来解决 Hedgehog 信号传导以及对 GC B 细胞自我更新或分化启动的影响的检查 GC 内的替代细胞谱系。评估刺猬分子影响的拟议实验 信号传导包括 GC B 细胞的 scRNAseq。