Antigen Recognition by Lymphocytes

描述(申请人提供)：严格控制动物体内淋巴细胞的特异性和数量，以避免自身免疫，并避免在先前感染期间产生的淋巴细胞积累。这种控制可以通过选择事件导致的自身反应淋巴细胞的死亡来实现。同样，许多为应对感染而产生的淋巴细胞在感染剂消失时死亡。淋巴细胞库也受到淋巴细胞改变其抗原受体的能力的影响。例如，一些自体反应性淋巴细胞表达的抗原受体可以通过删除编码有害受体的基因或通过沉默自体反应性受体的作用来修饰。 控制动物体内淋巴细胞的数量、特异性和活性，以避免在每次连续的感染反应中产生大量的淋巴细胞，并防止自身免疫。使用了几个过程来实现这种控制。许多为应对感染而产生的淋巴细胞在感染剂消失时死亡。一些自体反应性淋巴细胞死亡，另一些则通过删除编码违规受体的基因或以某种方式沉默自体反应性受体的活动来修改其受体的抗原。其他自身反应性淋巴细胞作为无能细胞存活一段时间，对抗原不产生反应，半衰期缩短。 该计划中的项目将研究淋巴细胞的控制方式，比较不同类型淋巴细胞在不同情况下使用的机制，目的是了解免疫系统如何产生有用但无害的抗原特异性淋巴细胞集合。个别项目的重点如下： 1.关于B细胞上的旁观者、非自身反应性受体的作用，以及它们拯救具有自身反应性受体的细胞免于死亡的能力。 2.关于无能B细胞的产生和维持、它们的特异性以及感染剂使这些细胞逃脱无能的能力。 3.探讨Bcl2相关蛋白在活化T、B细胞死亡中的作用。 该方案有4个核心，对所有项目的工作都是必不可少的。核心的主题是：流 细胞学；显微镜；遗传学和管理学。 项目1：B细胞存活和死亡的机制(Pelanda，R.) 项目1描述(申请人提供)：每天产生数百万个表达自身反应性抗体的B细胞。最近在小鼠身上的研究表明，新产生的未成熟B细胞与骨髓中的自身抗原发生反应，经历受体编辑和无能，并且受体编辑在外周保护性抗体库中贡献了很大一部分。这些最近的研究还表明，克隆删除，曾经被认为是中枢耐受的主要机制，可能是当自身反应性B细胞无法编辑其受体时进行的一种默认途径。自体反应性B细胞必须存活一段时间才能成功地编辑它们的受体，这是该模型的固有特性。自身反应性和非自身反应性未成熟B细胞的细胞存活差异最终控制了这些细胞的选择，并塑造了外周B细胞库。因此，我们认为，发生受体编辑的自身反应性未成熟B细胞的生存窗口对于开发保护性外周抗体库是绝对必要的。在受体编辑期间，什么生理上控制着未成熟B细胞的寿命尚不清楚，尽管可能涉及到抗和促凋亡途径的调节活动。除了受体编辑外，一个特异、有效和无害的B细胞库的产生也依赖于在非自身反应性BCR表达时阻止Ig基因进一步重排的信号，并介导免疫球蛋白等位基因/同型排斥。这些途径的功能障碍可能会导致过度的克隆性缺失，导致免疫缺陷，或者导致自身反应性B细胞存活，导致自身免疫。 现有证据表明，非自身反应性B细胞抗原受体的表达产生紧张性信号，对于非自身反应性(原发和编辑的，可能是无能的)未成熟B细胞的生存以及免疫球蛋白等位基因/同型排斥是重要的。我们认为，NF-B途径、BAFF-R信号转导途径和Bcl2家族信号转导途径可以正确地翻译B细胞抗原受体信号，从而调节细胞寿命和免疫球蛋白基因重组。我们已经创造了产生非自身反应性或自身反应性未成熟B细胞的小鼠品系，以及其他具有异常水平的BCR和BAFF-R表达的品系。利用这些生物学工具，我们建议确定NF-B通路和Bcl2家族如何调节原代未成熟B细胞的寿命，以及BCR和BAFF-R信号对细胞存活和建立Ig等位基因/同型排斥的相对贡献是什么。 这个项目将有助于我们理解是什么调节了发育中的B细胞的寿命，特别是取决于细胞是否具有自身反应。此外，我们的发现将揭示自身反应性B细胞逃避耐受并最终分化为自身抗体形成细胞的可能机制。

DESCRIPTION (provided by applicant): The specificities and numbers of lymphocytes in animals are tightly controlled to avoid autoimmunity and to avoid accumulation of lymphocytes generated during previous infections. This control can be achieved through the death of autoreactive lymphocytes as consequence of selection events. Similarly, many lymphocytes that are generated in response to infections die when the infectious agent disappears. The lymphocyte repertoire is also influenced by the ability of lymphocytes to alter their antigen receptor. For example, the antigen receptor expressed by some autoreactive lymphocytes can be modified either by deletion of the genes encoding the offending receptor, or by silencing the action of the autoreactive receptor. The numbers, specificities and activities of lymphocytes in animals are controlled, to avoid accumulation of the huge numbers of lymphocytes which are generated in each successive response to infection and to prevent autoimmunity. Several processes are used to achieve this control. Many of the lymphocytes which are generated in response to infections die when the infectious agent disappears. Some autoreactive lymphocytes die, others modify their receptors for antigen, either by deleting genes coding for the offending receptor, or by somehow silencing the action of the autoreactive receptor. Other autoreactive lymphocytes survive for a while as anergic cells and do not respond productively to antigen and have a shortened half life. The Projects in this Program will examine the ways in which lymphocytes are controlled, comparing the mechanisms used in different types of lymphocytes under different circumstances, with the goal of understanding how the immune system generates a useful but innocuous collection of antigen specific lymphocytes. The individual Projects will focus as follows: 1. On the role of bystander, non autoreactive receptors on B cells, and their ability to rescue cells bearing, in addition, autoreactive receptors from death. 2. On the generation and maintenance of anergic B cells, their specificities and the ability of infectious agents to allow these cells to escape anergy. 3. On the role of Bcl-2 related proteins in the death of activated T, and B cells. The Program has 4 Cores, all essential to the work on all Projects. The subjects of the Cores are: Flow Cytometry; Microscopy; Genetics and Administration. PROJECT 1: Mechanisms of B Cell Survival and Death (Pelanda, R.) PROJECT 1 DESCRIPTION (provided by applicant): Millions of B cells are generated daily that express autoreactive antibodies. Recent studies in mice indicate that newly generated immature B cells that react with autoantigens in the bone marrow undergo receptor editing and anergy, and that receptor editing contributes to a significant fraction of the peripheral protective antibody repertoire. These recent studies also suggest that clonal deletion, once thought the predominant mechanism of central tolerance, is probably a default pathway that is carried out when autoreactive B cells are unable to edit their receptors. It is intrinsic to this model that autoreactive B cells must survive for a certain amount of time in order to successfully edit their receptors. Differences in cell survival of autoreactive and non-autoreactive immature B cells ultimately control the selection of these cells and shape the peripheral B cell repertoire. Therefore, we propose that the window of survival of autoreactive immature B cells during which receptor editing takes place is absolutely essential for the development of a protective peripheral antibody repertoire. What physiologically controls the lifespan of immature B cells during receptor editing is not yet clear although likely involves the regulated activity of anti- and pro-apoptotic pathways. In addition to receptor editing, the generation of a specific, effective and innocuous B cell repertoire also relies on the signals that stop further Ig gene rearrangement upon expression of nonautoreactive BCRs and mediate immunoglobulin allelic/isotypic exclusion. Dysfunctions in these pathways may cause either excessive clonal deletion resulting in immunodeficiency or survival of autoreactive B cells resulting in autoimmunity. Available evidences indicate that the expression of non-autoreactive B cell antigen receptors generates tonic signals that are important for survival of non-autoreactive (primary and edited and possibly anergic) immature B cells as well as immunoglobulin allelic/isotypic exclusion. We propose that the NF-?B pathway, BAFF-R signaling and the Bcl-2 family properly translate B cell antigen receptor signaling to regulate cellular lifespan and immunoglobulin gene recombination. We have created mouse strains that generate either nonautoreactive or autoreactive immature B cells, and other strains that have abnormal levels of BCR and BAFF-R expression. Using these biological tools, we propose to determine how the NF-?B pathway and the Bcl-2 family regulate the lifespan of primary immature B cells, and what is the relative contribution of BCR and BAFF-R signaling to cell survival and establishment of Ig allelic/isotypic exclusion. This project will contribute to our understanding of what regulates the lifespan of developing B cells, in particular depending on whether the cells are autoreactive or not. Moreover, our findings will indicate possible mechanisms by which autoreactive B cells escape tolerance and eventually differentiate into autoantibody-forming cells.