Long-lived plasma cell differentiation

描述(由申请人提供)：这项建议使用模型小鼠系统来解决有关对病原体的长期体液免疫反应机制的基本问题。骨髓中的长寿命浆细胞(PC)负责建立保护性的终生体液免疫。充分了解长寿PC的分化机制是研制先进疫苗的关键。我们产生了IA-B小鼠，大约95%的B细胞上缺乏MHC-II，这是因为B细胞通过cd19cre Cre重组酶转基因限制了loxP侧翼的IAB neo等位基因的缺失。经T细胞依赖抗原免疫后，IA-B小鼠体内少量抗原特异性MHC-II+B细胞急剧扩增，分化为GC-B细胞，并使B220+CD38+记忆性B细胞水平正常。然而，由于CD19cre转基因持续缺失MHC-II，这些记忆B细胞后来失去了MHC-II的表达，从而为研究记忆B细胞依赖MHC-II的抗原递呈在体液免疫中的作用提供了一个独特的系统。与记忆B细胞上MHC-II的丢失有关，IA-B小鼠在长期存活的PC中显示出亲和力成熟受损。这里提出的假设是，记忆B细胞向长寿PC的分化需要MHC-II依赖的抗原提呈。1)通过体外培养纯化的VH转基因MHC-II阳性和MHC-II阴性的记忆B细胞，在模拟T细胞依赖或非T细胞非依赖刺激的刺激条件下，确定MHC-II在记忆B细胞功能中的内在要求；2)通过将纯化的VH转基因MHC-II阳性和MHC-II阴性的记忆B细胞过继转移到抗原经历或未经历受体的小鼠中，确定MHC-II在记忆B细胞PC分化途径中的作用。这些研究将确定记忆功能是否需要MHC-II，以及T细胞是否将记忆B细胞分化为PC。这将为进一步研究长期体液免疫的分子机制和“检查点”奠定基础。这一结果将对有效的疫苗开发以及治疗与自我反应性记忆B细胞的PC分化相关的自身免疫具有价值。疫苗接种会产生一小部分分泌保护性抗体的静息记忆B细胞和长寿的浆细胞。这项研究将测试记忆B细胞向长寿浆细胞的分化是否需要MHC-II，这是一种非常重要的与T细胞相互作用的分子。这项研究将进一步研究这种MHC-II分子对记忆B细胞功能的重要性，以便开发更好的疫苗接种。

DESCRIPTION (provided by applicant): This proposal employs model mouse systems to address fundamental questions regarding the mechanism of long-term humoral immune response to pathogens. Long-lived plasma cells (PCs) in bone marrow (BM) are responsible for establishing protective life-long humoral immunity. Fully understanding differentiation mechanism of long-lived PC is critical for advanced vaccine development. We generated IA-B mice that lack MHC-II on about 95% of all B cells due to B-cell-restricted deletion of a loxP-flanked iab neo allele by the cd19cre Cre recombinase transgene. Upon immunization with a T cell dependent antigen, a small number of antigen-specific MHC-II+ B cells in IA-B mice dramatically expand to differentiate into GC B cells and make normal level of B220+ CD38+ memory B cells. However, these memory B cells lose MHC-II expression later because of on-going deletion of MHC-II by the cd19cre transgene, thus providing a unique system to study the role of MHC-II-dependent antigen presentation by memory B cells in humoral immunity. In association with loss of MHC-II on memory B cells, IA-B mice showed impaired affinity maturation in long-lived PCs. The hypothesis proposed here is that differentiation of memory B cells into long-lived PCs requires MHC-II dependent antigen presentation. The specific aims to test our hypothesis are: 1) determine the intrinsic requirement MHC-II in memory B cells function, by in vitro culture of purified VH transgenic MHC-II positive and MHC-II negative memory B cells in the presence of various stimulation conditions simulating T cell dependent or T cell independent stimulation and 2) determine the role of MHC-II in PC differentiation pathway of memory B cells, by adoptive transfer of purified VH transgenic MHC-II positive and MHC-II negative memory B cells into antigen-experienced or un-experienced recipient mice. These studies will establish whether MHC- II is required for memory function and whether T cells direct memory B cell differentiation to PC. This will form the basis for further investigations to elucidate the molecular mechanism and 'checkpoints' in the pathway of long-term humoral immunity. The outcome will be valuable for effective vaccine development as well as treating autoimmunity associated with PC differentiation of self-reactive memory B cells. Vaccination generates a small fraction of resting-memory B cells and long-lived plasma cells secreting protective antibody. This study will test whether differentiation of memory B cells to long-lived plasma cells requires MHC-II, a very important molecule for interacting with T cells. This study will further examine how this MHC-II molecule is important for memory B cell function in order to develop better vaccination.