Manipulation of Follicular Helper T Cells in Immunity and Autoimmunity

描述（由申请人提供）：CD4 T细胞的帮助对于发生在次级淋巴器官（slo）生发中心（GCs）的B细胞产生抗体至关重要，这是免疫球蛋白（Ig）亲和成熟和同型转换的位点。在GCs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，它们是B细胞选择成熟为记忆B细胞和长寿命抗体分泌（血浆）细胞所必需的。Tfh细胞可与其他CD4效应细胞区分；例如，Th1， Th2和Th17子集（以及其他），通过它们的GC位置和作为B细胞辅助器的功能。Tfh细胞在正常和自身免疫反应中对B细胞的帮助至关重要；然而，与其他CD4 T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，我们设计了一种在正常和异常免疫反应期间选择性标记和/或删除这些细胞的方法。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）的抑制剂ectodin在其他免疫细胞中由Tfh细胞选择性表达。在这里，我们提出了一个体内系统的发展，专门针对和操纵Tfh细胞使用外泌素启动子。我们建议构建一种他莫昔芬诱导的Cre小鼠，其中Cre与雌激素受体ERT2融合，将在外泌素基因（Sostdc1）下游表达；靶向构建体已经制作完成，序列验证，纯化，并微注射到胚胎干细胞中。当与适当的报告菌株（如Rosa-26-YFP）、缺失菌株（R-DTA小鼠）或表达两个loxP位点的靶基因的菌株杂交时，它将使我们能够特异性地跟踪或消融Tfh细胞，或在免疫或自身免疫反应期间所需的时间点产生Tfh特异性基因缺失；后者将通过将我们的诱导Cre小鼠与合适的狼疮易感菌株杂交来完成。目前还没有办法特异性地靶向和分析Tfh细胞在免疫应答中的作用；因此，我们相信我们创造可诱导的Tfh细胞特异性Cre小鼠的方法将为研究Tfh生物学的不同方面开辟机会。

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. PUBLIC HEALTH RELEVANCE: Subset of T cells, follicular helper T cells, is necessary for helping B lymphocytes produce antibodies and autoantibodies in normal and autoimmune responses. Much remains to be learned about the biology of the former, including the requirements for their maturation and function, and how to interrupt their collaboration with B cells as a potential therapy for autoimmune diseases. The results of the proposed studies should help address these issues, and advance knowledge of how autoimmune responses develop in humans.