B Cell Developmental Defect in Murine Lupus

描述(由研究人员提供)：在NZB/WF1模型中已经描述了多个B细胞缺陷，但除了作为自身抗体产生者外，它们在狼疮发病中的具体作用尚不清楚。限制因素之一是复杂的遗传背景要求，包括H-2z等位基因，这限制了试剂的可获得性和功能实验。我们已经用3个NZM2410衍生的SLE基因组基因座建立了一个新的狼疮模型，这些基因座对于B6背景下的疾病诱导是必要和充分的。这种三重同源基因的B6TC株由大约94%的B6基因组组成，但仍发展为完全穿透性狼疮性肾炎。B6.TC小鼠表现出与NZM2410相同的B细胞发育缺陷，包括B1a细胞在腹膜腔内堆积和脾内浆细胞堆积，这是由于对CXCR12缺乏反应性，CXCR12通常将PC迁移到骨髓。我们建议使用B6.TC模型来描述这两个发育B细胞缺陷的遗传学和机制，并确定它们在狼疮发病中的作用。此外，我们建议在B6.TC上培育BCRTG，以比较该菌株的B细胞耐受机制与Fas缺陷模型的机制。为了实现这一目标，我们有三个具体的目标：1.研究B6.TC小鼠中perc B1a蓄积的机制，并评价其在发病机制中的作用。我们假设B1Aperc在B6.TC小鼠体内的积聚是由固有的B1a细胞缺陷和来自非B细胞室的异常调节造成的。我们预测，这一调控涉及STAT4信号转导，因为STAT4缺乏阻止了B6.TC中perc B1a的积累。这些假设将得到评估，每个SLE基因座的贡献将在此过程中得到评估。最后，我们将讨论Perc B1a细胞对自身抗体生产和临床混合BM嵌合体的贡献。2.探讨B6-TC脾PC蓄积的功能和遗传机制。我们假设这种缺陷是由于PC分化过程中固有的B细胞缺陷和非B细胞因子造成的，这些因素创造了支持脾中大量长寿PC维持的“生存环境”。我们认为这些因子涉及B6.TC T细胞过度表达的CD40L和IL-4。此外，STAT6缺乏可恢复正常的B6、TC、PC向脾的迁移。我们建议检验这些假说，并评估每个SLE基因座在这一过程中的贡献。3.利用RF特异的AM14H转基因动物模型，探讨B细胞耐受丧失的机制。B6.TC小鼠自发产生类风湿因子。我们建议使用产生抗IgG2aa RF的AM14H TG来探索B6.TC模型中B细胞耐受性丧失的机制，并与Fas缺陷模型中描述的机制进行比较。这个B6.TC.AM14将构成一个非常有价值的工具，在Fas完整的自身免疫模型中跟踪自身反应性B细胞的命运和发展。

DESCRIPTION (provided by investigator): Multiple B cell defects have been described in the NZB/WF1 model, but their specific role in lupus pathogenesis is unclear, beyond their role as autoantibody producers. One of the limiting factors has been the requirement of a complex genetic background, including the H-2z allele, which has restricted reagent availability and functional experiments. We have produced a new model of lupus with the 3 NZM2410-derived Sle genomic loci that are necessary and sufficient for disease induction on a B6 background. This triple congenic B6.TC strain is constituted by approximately 94% of B6 genome, but yet develops a fully penetrant lupus nephritis. B6.TC mice show the same B cell developmental defects as NZM2410, which include an accumulation of B1a cells in the peritoneal cavity and a splenic accumulation of plasma cells, due to an absence of responsiveness to CXCR12, which normally directs PC migration to the bone marrow. We propose to use the B6.TC model to characterize the genetics and the mechanisms of these two developmental B cell defects, and determine their role in lupus pathogenesis. In addition, we propose to breed a BCR Tg on B6.TC to compare the mechanisms of B cell tolerance in that strain to that of the FAS-deficient model. To accomplish this goal, we have three specific aims: 1. To characterize the mechanisms of PerC B1a accumulation in B6.TC mice, and to assess its role in pathogenesis. We hypothesize that B1a PerC accumulation in B6.TC mice results from intrinsic B1a cell defects and from an abnormal regulation from a non-B cell compartment. We predict that this regulation involves STAT4 signaling as STAT4 deficiency prevents PerC B1a accumulation in B6.TC. These hypotheses will be assessed, and the contribution of each Sle locus will be evaluated in the process. Finally, we will address the contribution of PerC B1a cells to autoAb production and clinical with mixed BM chimeras. 2. To determine the functional and genetic mechanisms leading to PC accumulation in B6.TC spleens. We hypothesize this defect results from intrinsic B cell defects during PC differentiation and non-B cell factors that create "survival niches" that support the maintenance of large number of long-lived PC in the spleen. We propose that these factors involve CD40L and IL-4, which are over-expressed by B6.TC T cells. Moreover, STAT6 deficiency restores normal B6.TC PC migration to the spleen. We propose to test these hypotheses and assess the contribution of each Sle locus in the process. 3. To determine the mechanisms responsible for the loss of B cell tolerance using the RF-specific AM14 H transgenic model. B6.TC mice spontaneously produce rheumatoid factor. We propose to use the AM14 H Tg that produce anti-IgG2aa RF to explore the mechanisms of loss of B cell tolerance in the B6.TC model, comparatively to the mechanisms described in the FAS deficient model. This B6.TC.AM14 will constitute a very valuable tool to track the fate and development of autoreactive B cells in a FAS intact autoimmune model.