Toll-like receptor signaling in the generation of B1b cell memory

B1b 细胞记忆生成中的 Toll 样受体信号传导

• 批准号: 8524050
• 负责人: KISHORE R ALUGUPALLI
• 金额: $ 38.75万
• 依托单位: THOMAS JEFFERSON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-15 至 2014-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8524050
• 关键词: Adaptor Signaling Protein; Affect; Agammaglobulinaemia tyrosine kinase; Agonist; Antibody Formation; Antigens; B-Lymphocytes; Bacteremia; Bacteria; Bacterial Polysaccharides; Borrelia; Cause of Death; Cells; Cloaca Chamber; Communicable Diseases; Data; Dextrans; Enterobacter cloacae; Environment; Exhibits; Experimental Models; Family; Ficoll; Frequencies; Generations; Genes; Homeostasis; Immune response; Immune system; Immunity; Immunization; Immunodeficient Mouse; In Vitro; Infection; Kinetics; Life; Link; Longevity; Maintenance; Mature B-Lymphocyte; Measures; Memory; Memory B-Lymphocyte; Metabolic; Modeling; Molecular; Morbidity - disease rate; Mus; Mutation; Phosphotransferases; Plasma Cells; Play; Polysaccharides; Receptor Signaling; Receptors, Antigen, B-Cell; Recurrence; Resistance; Resolution; Role; Signal Pathway; Signal Transduction; T-Lymphocyte; TALL-1 protein; Testing; Time; Toll-like receptors; Transgenic Mice; Up-Regulation; Vaccination; Vaccines; base; crosslink; dextran; fitness; in vivo; member; mortality; novel; novel strategies; pathogen; receptor; receptor-mediated signaling; response

DESCRIPTION (provided by applicant): Infectious diseases are the leading cause of death worldwide and vaccination is the most effective means to control them. Persistence of memory B cells generated by vaccination is critical for the longevity of protective immunity, but the molecular mechanism required for their long-term maintenance is unknown. B cell responses generated in the absence of T cell-help had been considered short-lived and inefficient in generating B cell memory. Using the experimental model of Borrelia hermsii bacteremia, we discovered a novel role for B1b cells, a subset of mature B cells, in long-lasting memory responses in the absence of T cell-help. Specifically, we found that B1b cells expand concurrently with the resolution of B. hermsii bacteremia and persist for long time. B1b cells from convalescent mice but not from na¿ve mice generate a specific antibody response and confer long-lasting immunity, indicating that the protective response corresponds to B1b cell expansion and persistence as in the case of conventional B cell memory. B cell responses to T cell-independent antigens such as bacterial polysaccharides are generated primarily by cross-linking B cell antigen receptors (BCR). Although Pneumococcal polysaccharide is also recognized by B1b cells, it does not induce antibody responses in X-linked immunodeficient mice (xid) mice, which have a mutation in gene encoding for Bruton's tyrosine kinase (Btk), which is required for optimal BCR-mediated signaling. In contrast, B. hermsii induces not only a specific antibody response but also a selective expansion of B1b cells in xid mice. These expanded B1b cells persist for long time, conferring upon the convalescent xid mice resistance to re-infection. These data suggest that immunostimulatory mechanisms other than BCR signaling can play an important role in the generation and maintenance of T cell-independent B1b cell memory. We found that B. hermsii is capable of activating Toll-like receptors (TLRs) and mice deficient in both Btk and MyD88, an adaptor protein required by multiple members of the TLR family, are severely impaired in mounting protective responses indicating that a coordinated signaling through BCR and TLR is critical. We have also found that TLR and BCR signaling pathways synergize to upregulate BR3 and TACI, the major receptors for B Lymphocyte Stimulator (BLyS, also known as BAFF), on B1b cells in vitro. Furthermore, we found that immunization with whole bacteria also induces BR3 up-regulation on expanded antigen-specific B1b cells in vivo. BLyS, by engaging BR3, induces the expression of the pro-survival molecules Mcl-1 and Bcl-XL and kinases involved in cellular metabolic fitness and B cell homeostasis. These findings led us to hypothesize that B1b cells that have responded to both BCR and TLR stimulation express higher levels of BR3 and TACI and are preferentially maintained over na¿ve B cells or B cells that are stimulated by BCR cross-linking alone as in the case of plain polysaccharide antigens. Identifying the role of TLR and BLyS signaling in B1b cell expansion and long-term maintenance will provide novel approaches for the generation of effective vaccines.

描述(申请人提供)：传染病是全球主要的死亡原因，接种疫苗是控制这些疾病的最有效手段。疫苗接种产生的记忆B细胞的持久性对于保护性免疫的长寿至关重要，但其长期维持所需的分子机制尚不清楚。在没有T细胞帮助的情况下产生的B细胞反应被认为是短暂的，在产生B细胞记忆方面效率低下。利用赫氏疏螺旋体菌血症的实验模型，我们发现在缺乏T细胞帮助的情况下，B1B细胞(成熟B细胞的一个子集)在长期记忆反应中发挥了新的作用。具体地说，我们发现B1B细胞与Hermsii菌血症的溶解同时扩张，并持续很长时间。来自恢复期小鼠的B1B细胞而不是来自初治小鼠的B1B细胞产生特异性抗体反应并提供持久的免疫，表明这种保护性反应与B1B细胞的扩张和持久性相对应，就像传统的B细胞记忆情况一样。B细胞对细菌多糖等T细胞非依赖性抗原的反应主要是通过交联型B细胞抗原受体(BCR)产生的。虽然肺炎球菌多糖也被B1B细胞识别，但它不能在X连锁免疫缺陷小鼠(XID)小鼠中诱导抗体反应，XID小鼠编码Bruton‘s酪氨酸激酶(BTK)的基因发生突变，BTK是最佳BCR介导的信号传递所必需的。相反，在XID小鼠中，Hermsii不仅能诱导特异性抗体反应，还能选择性地扩增B1B细胞。这些扩大的B1B细胞持续很长时间，使正在康复的XID小鼠对再次感染具有抵抗力。这些数据表明，BCR信号以外的免疫刺激机制可能在T细胞非依赖性B1B细胞记忆的产生和维持中发挥重要作用。我们发现，Hermsii能够激活Toll样受体(TLRs)，并且BTK和MyD88(TLR家族中多个成员所需的适配器蛋白)缺陷的小鼠在建立保护反应方面受到严重损害，这表明通过BCR和TLR的协调信号是至关重要的。我们还发现，TLR和BCR信号通路在体外协同上调B1B细胞上的B淋巴细胞刺激因子(BLyS，又称BAFF)的主要受体BR3和TACI。此外，我们还发现，在体内，全菌免疫也能诱导BR3上调扩增的抗原特异性B1B细胞。BLyS通过与BR3结合，诱导促进生存的分子Mcl-1和Bclxl的表达，以及参与细胞代谢适应性和B细胞动态平衡的激酶的表达。这些发现导致我们假设，对BCR和TLR刺激都有反应的B1B细胞表达更高水平的BR3和TACI，并且比BCR交联物单独刺激的B细胞优先保持，就像在普通多糖抗原的情况下一样。确定TLR和BLyS信号在B1B细胞扩增和长期维持中的作用将为生产有效的疫苗提供新的途径。