Manipulation of Follicular Helper T Cells in Immunity and Autoimmunity

描述(由申请人提供)：CD4T细胞帮助B细胞产生抗体，抗体发生在次级淋巴器官(SLO)的生发中心(GC)，是免疫球蛋白(Ig)亲和成熟和同型转换的部位。在GC中，T滤泡辅助细胞(TFH)为B细胞提供生存和分化信号，包括CD40配体(CD40)、程序性死亡受体-1(PD-1)和IL-21，对于成熟为记忆性B细胞和长寿抗体分泌(浆)细胞的B细胞的选择是必不可少的。TFH细胞可以通过它们的GC位置和作为B细胞助手的功能来区别于其他CD4效应细胞，例如Th1、Th2和Th17亚群(以及其他)。无论是在正常反应还是自身免疫反应中，TFH细胞对B细胞HELI都是至关重要的；然而，与其他CD4T效应细胞亚群相比，这些细胞的发育和功能尚不清楚。为了解决这个问题，我们设计了一种方法，在正常和异常免疫反应期间按时间顺序选择性地标记和/或删除这些细胞。为了实现这一目标，我们将利用我们最近的观察结果，即骨形态发生蛋白(BMPs)的抑制因子ectodin在其他免疫细胞中由TFH细胞选择性表达。在这里，我们建议开发一种体内系统，利用ectodin启动子来特异性地靶向和操纵TFH细胞。我们建议制造一种三苯氧胺诱导的Cre小鼠，其中Cre与雌激素受体ERT2融合，将在ectodin基因(Sostdc1)的下游表达；靶向构建已经完成，序列验证，纯化，并显微注射到胚胎干细胞中。当与适当的报告株(例如ROSA-26-YFP)、Deleter株(R-DTA小鼠)或表达靶基因的株(S)杂交时，它将允许我们特异性地跟踪或去除TFH细胞，或在免疫或自身免疫反应期间产生TFH特异性基因缺失；后者将通过将我们可诱导的CRE小鼠与适当的狼疮易感株杂交来实现。目前还没有办法专门针对和分析TFH细胞在免疫反应中的作用；因此，我们相信我们创造一种可诱导的TFH细胞特异性Cre小鼠的方法将为研究TFH生物学的不同方面打开机会。

DESCRIPTION (provided by applicant): CD4 T cell help is crucial for B cell production of antibodies that occurs in germinal centers (GCs) of secondary lymphoid organs (SLOs), a site of immunoglobulin (Ig) affinity maturation and isotype switching. In GCs, T follicular helper (Tfh) cells provide B cells with survival and differentiation signals, including CD40 ligand (CD40), programmed death receptor-1 (PD-1), and IL-21, essential for B cell selection with maturation into memory B cells and long-lived antibody-secreting (plasma) cells. Tfh cells can be distinguished from other CD4 effector cells; e.g., the Th1, Th2, and Th17 subsets (among others), by their GC location and function as B cell helpers. Tfh cells are critical for B cell hel in both normal and autoimmune responses; yet, the development and function of these cells, compared to other CD4 T effector cell subsets, is less clear. To address this issue, we have devised an approach to selectively mark and/or delete these cells chronologically during normal and aberrant immune responses. To accomplish this goal, we will take advantage of our recent observation that ectodin, an inhibitor of bone morphogenetic proteins (BMPs), is selectively expressed by Tfh cells among other immune cells. Here we propose the development of an in vivo system to specifically target and manipulate Tfh cells using the ectodin promoter. We propose to make a tamoxifen-inducible-Cre mouse in which Cre, fused with the estrogen receptor ERT2, will be expressed downstream of the ectodin gene (Sostdc1); the targeting construct has already been made, sequence verified, purified, and micro-injected into embryonic stem cells. When crossed with the appropriate reporter strain (e.g., Rosa-26-YFP), deleter strain (R-DTA mouse) or with strain(s) that expresses a target gene flanked by two loxP sites, it will allow us to specifically track or ablate Tfh cells, or engender a Tfh- specific deletion of genes a desired time points during an immune or autoimmune response; the latter will be accomplished by crossing our inducible Cre mouse with appropriate lupus-prone strains. Currently there is no way to specifically target and analyze the role of Tfh cells in immune responses; thus, we believe our approach of creating an inducible, Tfh cell-specific Cre mouse will open up opportunities to study different aspects of Tfh biology.