The role of TIM-1 and Regulatory B cells in Allograft Tolerance

描述(由申请人提供)：现在很清楚，B细胞可以通过依赖IL-10的方式发挥重要作用，下调免疫反应。除了在体外刺激后表达IL-10的能力外，这些罕见的调节性B细胞(BREG)缺乏特定的标志物，存在于各种B细胞亚群中，其频率可低至1%。这使得对布雷格的研究具有挑战性。令人惊讶的是，一些被认为通过对T细胞的作用来诱导同种异体移植耐受的药物，最近被证明是B细胞依赖的。这表明BREG可能参与了同种异体移植耐受，并在其中发挥了广泛的作用。这与在耐受性人类肾移植受者中观察到的“B细胞特征”相呼应。T细胞Ig粘蛋白-1有助于调节Th的分化。抗TIM-1(RMT1-10)诱导同种异体移植耐受，被认为是Th2依赖的。令人惊讶的是，我们发现TIM-1在B细胞上的表达水平远远高于T细胞。此外，抗TIM-1诱导的Th2偏离和同种异体移植耐受完全依赖于B细胞。事实上，在没有B细胞的情况下，与未经治疗的对照组相比，抗TIM-1实际上加速了排斥反应。在所有主要亚群中，绝大多数IL-10+和IL-4+B细胞都表达TIM-1。来自同种异体移植受者的TIM-1+，而不是TIM-1-，B细胞可以将耐受性转移给未经治疗的同种异体移植受者。最后，抗Tim-1显著诱导IL-10+(Tim-1+)Breg，但Breg的形成和诱导都需要IL-4信号转导。有了这些新的见解，我们现在可以确定TIM-1+BREG同种异体移植耐受的作用，并确定TIM-1在BREG生成中的作用。具体地说，在目标1中，我们将通过TIM-1功能丧失(LOF)KI小鼠来确定TIM-1+Breg在同种异体移植耐受中的作用，并确定TIM-1+B细胞是否是由各种其他介质介导的耐受所需的特定B细胞群。在目标2中，我们将确定B效应细胞、Th2细胞和Treg在Breg诱导和抗Tim-1介导的耐受中的作用。在目标3中，我们将研究通过TIM-1诱导BREG的机制，确定同源抗原识别和特定细胞因子信号的作用。我们相信，这些研究将极大地提高我们对BREG免疫生物学的了解，并提供与同种异体移植耐受高度相关的治疗见解。

DESCRIPTION (provided by applicant): It is now clear that B cells can play an important role downregulating immune responses in an IL-10-dependent fashion. Other than a capacity to express IL-10 after ex vivo stimulation, these rare regulatory B cells (Breg) lack specific markers and are found within various B cell subpopulations where their frequency can be as low as 1%. This has made study of Breg challenging. Surprisingly, a number of agents believed to induce allograft tolerance through their effects on T cells, were recently shown to be B cell dependent. This suggests that Breg may be involved, and play a broad role in allograft tolerance. This is echoed by the "B cell profile" observed in tolerant human renal allograft recipients. T cell Ig Mucin protein-1 helps regulate Th differentiation. Anti- TIM-1 (RMT1-10) induces allograft tolerance thought to be Th2 dependent. Surprisingly, we found TIM-1 is expressed at much higher levels on B than T cells. Moreover, Th2 deviation and allograft tolerance induced by anti-TIM-1, were completely B cell dependent. In fact, in the absence of B cells, anti-TIM-1 actually accelerates rejection compared to untreated controls. TIM-1 is expressed by the large majority of IL-10+ and IL-4+ B cells in all major subpopulations. TIM-1+, but not TIM-1-, B cells from allograft recipients can transfer tolerance to otherwise untreated allograft recipients. Finally, anti-TIM-1 significantly induces IL-10+ (TIM-1+) Breg, but both Breg development and induction require IL-4 signaling. Armed with these novel insights, we can now establish the role of TIM-1+ Breg allograft tolerance and determine the role of TIM-1 in Breg generation. Specifically, In Aim 1, we will define the role of TIM-1+ Breg in allograft tolerance using TIM-1 loss of function (LOF) KI mice, and determine whether TIM-1+ B cells are the specific B cell population required for tolerance mediated by various other agents. In Aim 2, we will define the roles of B effector cells, Th2 cells, and Treg in Breg induction and anti-TIM-1 mediated tolerance. In Aim 3 we will examine the mechanisms of Breg induction through TIM-1, identifying the role of cognate Ag recognition and specific cytokine signals. We believe these studies will greatly enhance our understanding of Breg immunobiology and provide therapeutic insight highly relevant to allograft tolerance.