Visualization of individual Foxp3+ T cells during an onset and progression of aut

描述（由申请人提供）：本提案的主要目标是确定在胸腺中避免负选择的自身反应性T细胞可以击败周围的调节性CD4+Foxp3+ T细胞的情况。我们认为，为了实现这一目标，有必要研究个体自身反应性和调节性T细胞在其自然环境中的特征。此外，这些细胞必须表达针对自身和非自身抗原的不同抗原受体（TCRs）。为此，我们最近建立了一种独特的体内模型，其中所有T细胞都表达一种多克隆但受限的TCRs （TCRmini小鼠）。在该模型中，TCRs的CDR3区域可用于追踪自身免疫性疾病不同阶段的单个幼稚、效应和调节性T细胞。现在我们也报告了我们已经开发了两种体内模型，其中表达TCR迷你库的T细胞产生全身或器官特异性自身免疫。随后，我们将研究抗原特异性自身反应性和调节性Foxp3+ CD4+ T细胞克隆之间的平衡如何被破坏，从而导致自身免疫反应的发生。在特异性目标1中，我们建议确定天然和适应性TR细胞是否在自身免疫性疾病的发生和进展中发挥不同的作用。我们还假设，虽然一些天然的TR细胞表达自身反应性tcr，并可能失去Foxp3的表达，但这些残疾的TR细胞在自然自身免疫反应中的参与是微不足道的。我们的第二个特异性目标将检查自身反应性T细胞的克隆逃逸是由少数对自身MHC/肽复合物具有更高TCR亲和力的克隆驱动的，还是由自身反应性T细胞的内在更高频率引起的。我们的目标还将是揭示个体自身反应性T细胞克隆对TR细胞抑制的抵抗力是否不同。在我们的第三个特异性目标中，我们将研究是否经过抗原处理的Foxp3+ TR细胞比未经过抗原处理的Foxp3+细胞表现出更好的抑制能力，以及它们的TCR库是否比在没有抗原处理的Foxp3+细胞上发现的TCR库更寡克隆。本研究的重点是研究天然和适应性Foxp3+调节性T淋巴细胞诱导耐受的机制。这些调节性T淋巴细胞监督其他免疫细胞的功能，并控制自身反应性T细胞防止自身免疫的发生。更好地了解自身反应性细胞克服CD4+Foxp3+细胞调节功能的机制，对于开发更好的治疗自身免疫性疾病的治疗策略至关重要。

DESCRIPTION (provided by applicant): The main goal of this proposal is to determine the circumstances under which autoreactive T cells that have avoided negative selection in the thymus can defeat regulatory CD4+Foxp3+ T cells in the periphery. In our opinion, to achieve this goal it is necessary to study the features of individual autoreactive and regulatory T cells in their natural environment. In addition, these cells must express different antigen receptors (TCRs) specific for both self and non-self antigens. For this purpose, we have recently established a distinctive in vivo model where all T cells express a polyclonal but restricted repertoire of TCRs (TCRmini mice). In this model the CDR3 regions of TCRs can be used to trace individual naove, effector, and regulatory T cells in different stages of autoimmune disease. Now we also report that we have developed two in vivo models where T cells expressing this TCR mini- repertoire develop systemic or organ-specific autoimmunity. Subsequently, our proposal will investigate how the balance between antigen specific autoreactive and regulatory Foxp3+ CD4+ T cells clones can be destroyed, leading to the onset of autoimmune responses. In Specific Aim 1 we propose to determine if natural and adaptive TR cells play a distinctive role during onset and progression of autoimmune disease. We also hypothesize that though some natural TR cells express autoreactive TCRs and may lose Foxp3 expression the participation of these disabled TR cells in natural autoimmune responses is insignificant. Our second Specific Aim will examine if clonal escape of autoreactive T cells is driven by a few clones with higher TCR affinity for self MHC/peptide complexes or is caused by intrinsically higher frequency of autoreactive T cells. Our objective will also be to reveal if individual autoreactive T cell clones differ in their resistance to suppression by TR cells. In our third Specific Aim we will investigate if antigen-experienced Foxp3+ TR cells exhibit improved suppressor ability compared to naove Foxp3+ cells, and whether their TCR repertoire is more oligoclonal than the TCR repertoire found on the antigen-inexperienced Foxp3+ cells. PUBLIC HEALTH RELEVANCE This proposal focuses on investigating the mechanisms of tolerance induction by natural and adaptive Foxp3+ regulatory T lymphocytes. These regulatory T lymphocytes supervise the function of other immune cells and control autoreactive T cells preventing onset of autoimmunity. Better understanding of the mechanisms that autoreactive cells utilize to override regulatory function of CD4+Foxp3+ cells is critical for the development of better therapeutic strategies to treat autoimmune diseases.