Intestinal Mucosal Immunity

许多急性病毒感染诱导不依赖于早期T细胞的多克隆B细胞活化和 在经典的T细胞依赖性B生发中心形成之前，抗原特异性伊加或IgG。然而，在这方面， 启动早期T细胞非依赖性类别转换重组（CSR）的必要信号尚不清楚。 本申请的目的是确定驱动T细胞非依赖性B细胞增殖的基本途径。 激活和伊加CSR。 我们建议利用轮状病毒感染的小鼠模型，其中派伊尔集合淋巴结（PP）T细胞非依赖性 在病毒暴露后48小时内诱导多克隆B细胞活化，随后产生轮状病毒。 特异性伊加。轮状病毒体外诱导B细胞活化需要树突状细胞。轮状病毒抗原存在于 PP树突状细胞在体内，这些细胞在B细胞活化时被活化，这表明， 树突细胞是B细胞对轮状病毒应答的重要调节剂。我们发现B细胞活化是 依赖于轮状病毒颗粒的结构完整性，表明轮状病毒诱导 树突状细胞反应作为模式识别的结果。初步实验表明，缺乏 MyD 88表达导致B细胞活化的消除和肠伊加水平的显著降低。 我们发现B细胞活化因子（BAFF）信号通路的突变也导致B的消融 细胞激活，表明MyD 88和BAFF之间的潜在联系。PP B细胞后数天 活化后PP中TGF-β表达和伊加+ B细胞数量增加，提示TGF-β 在PP对轮状病毒的多克隆应答中也起重要作用。因此，我们假设， 树突状细胞调节快速T细胞非依赖性病原体特异性抗体的产生， PP通过诱导多克隆B细胞反应，该反应由MyD 88、BAFF和TGF-β引起。 信号传导独立于抗原特异性BCR。我们将通过体外和体内试验来检验这一假设。 vivo的方法追求以下三个目标： 目标1.确定轮状病毒是否诱导树突状细胞MyD 88信号传导驱动B细胞 应答 目标2.确定MyD 88信号传导是否导致BAFF和TGF-β产生。 目标3。描述多克隆B细胞对轮状病毒的反应。 本申请中提出的研究对于解决关于 肠中T细胞非依赖性抗体诱导的分子机制。这项工作将提供新的 深入了解肠道免疫反应以及有助于改进粘膜疫苗策略。 确定病原体如何诱导快速但特异的抗体具有巨大的潜力，可以确定早期 抗体限制病毒复制和传播，并提供保护。

Many acute viral infections induce early T cell independent polyclonal B cell activation and production of antigen-specific IgA or IgG prior to the formation of classical T cell dependent B germinal centers. However, the necessary signals for initiation of early T cell independent class switch recombination (CSR) are not known. The objective of this application is to determine the essential pathways that drive T cell independent B cell activation and IgA CSR. We propose to utilize the murine model of rotavirus infection in which Peyer's patch (PP) T cell independent polyclonal B cell activation is induced within 48 hours after viral exposure followed by production of rotavirus- specific IgA. Rotavirus induced B cell activation in vitro requires dendritic cells. Rotavirus antigen is present in PP dendritic cells in vivo and these cells are activated at the time B cell activation occurs, suggesting that dendritic cells are important modulators of the B cell response to rotavirus. Our finding that B cell activation is dependent on the structural integrity of the rotavirus particles suggested the possibility that rotavirus induces dendritic cell responses as a result of pattern recognition. Preliminary experiments demonstrate that lack of MyD88 expression results in an ablation of B cell activation and substantial reduction in intestinal IgA levels. We find that a mutation in the B cell activating factor (BAFF) signaling pathway also results in the ablation of B cell activation, suggesting a potential link between MyD88 and BAFF. Several days following PP B cell activation there is an increase of TGF-¿ expression and numbers of IgA+ B cells in the PP, suggesting TGF-¿ also plays an important role in the PP polyclonal response to rotavirus. Therefore, we hypothesize that dendritic cells modulate the production of rapid T cell independent pathogen-specific antibody in the PP through induction of a polyclonal B cell response that results from MyD88, BAFF, and TGF-¿ signaling independent of an antigen-specific BCR. We will test this hypothesis by using both in vitro and in vivo approaches to pursue the following three aims: Aim 1. Determine whether rotavirus induces dendritic cell MyD88 signaling that drives B cell responses. Aim 2. Determine whether MyD88 signaling results in BAFF and TGF-ss production. Aim 3. Characterize the polyclonal B cell responses to rotavirus. The studies proposed in this application are of importance in addressing unanswered questions regarding the molecular mechanisms of T cell independent antibody induction in the intestine. This work will provide new insights into intestinal immune responses as well as contribute to improved mucosal vaccine strategies. Defining how pathogens induce rapid but specific antibody has tremendous potential to define the role of early antibody in limiting viral replication and dissemination and providing protection.