Long-lived plasma cell differentiation

描述（由申请方提供）：本提案采用模型小鼠系统来解决有关对病原体的长期体液免疫应答机制的基本问题。骨髓（BM）中的长寿浆细胞（PC）负责建立保护性终身体液免疫。深入了解长寿命PC的分化机制是进一步开发疫苗的关键。我们产生了IA-B小鼠，由于cd 19 cre Cre重组酶转基因导致loxP侧翼的iab neo等位基因的B细胞限制性缺失，约95%的所有B细胞上缺乏MHC-II。在用T细胞依赖性抗原免疫后，IA-B小鼠中的少量抗原特异性MHC-II+ B细胞显著扩增以分化为GC B细胞，并使B220+ CD 38+记忆B细胞达到正常水平。然而，这些记忆B细胞由于通过cd 19 cre转基因持续缺失MHC-II而随后失去MHC-II表达，从而提供了一个独特的系统来研究记忆B细胞在体液免疫中的MHC-II依赖性抗原呈递的作用。与记忆B细胞上MHC-II的缺失相关，IA-B小鼠在长寿命PC中表现出亲和力成熟受损。这里提出的假设是，记忆B细胞分化为长寿的PC需要MHC-II依赖性抗原呈递。检验我们假设的具体目标是：1）通过在模拟T细胞依赖性或T细胞非依赖性刺激的各种刺激条件存在下体外培养纯化的VH转基因MHC-II阳性和MHC-II阴性记忆B细胞，确定记忆B细胞功能中MHC-II的内在要求，和2）确定MHC-II在记忆B细胞的PC分化途径中的作用，通过将纯化的VH转基因MHC-II阳性和MHC-II阴性记忆B细胞过继转移到抗原经历或未经历的受体小鼠中。这些研究将确定MHC-II是否是记忆功能所必需的，以及T细胞是否指导记忆B细胞分化为PC。这将为进一步研究阐明长期体液免疫途径中的分子机制和“检查点”奠定基础。该结果对于有效的疫苗开发以及治疗与自身反应性记忆B细胞的PC分化相关的自身免疫将是有价值的。疫苗接种产生一小部分静息记忆B细胞和分泌保护性抗体的长寿浆细胞。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，这是一种与T细胞相互作用的非常重要的分子。本研究将进一步研究MHC-II分子对记忆B细胞功能的重要性，以开发更好的疫苗。

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.