BCR regulation of antibody responses

描述（由申请方提供）：B细胞抗原受体（BCR）的信号传导由抗原结合诱导，并通过关键负调控分子水平或活性的动态变化以定量和定性方式进行调控。我们假设这种调节对于提供抗体应答的最佳控制是至关重要的， 限制自身反应性并促进高质量抗体的产生。在由BCR激活的主要信号传导途径中，是磷脂酶Cg 2的激活，其产生第二信使二酰基甘油（DG）和三磷酸肌醇。拟议的研究集中在DG水平的调节膜的二酰基甘油激酶（DGKs）。我们已经发现，DGKa和DGKz似乎是淋巴细胞中这种负调节因子的两种主要形式，随着B细胞在脾中成熟而上调，并且在抗原诱导的成熟B细胞活化后不久下调。这些和其他观察结果表明，DGK的动态调节在调节B细胞活化阈值中起重要作用。 我们已经表征了DGKa或DGKz的消融对成熟B细胞中DG信号传导的影响，并且发现DGKz是关键调节器，而DGKa起次要作用。为了响应T细胞非依赖性2型抗原，DGKz-/-小鼠产生更大、更快的抗体反应。此外，DGKz-/- B细胞对T细胞依赖性抗原的应答也增加，特别是关于早期滤泡外浆细胞的产生。这些研究表明，BCR诱导的DG信号的量提供了早期浆细胞反应的亲和力歧视。 所提出的研究将确定在B细胞中DGKz减弱DG信号传导对于宿主防御流感病毒感染的生物学意义（具体目的1）;将检验以下假设： 由等位基因系列中Erk 1和Erk 2的一些但非全部等位基因的缺失导致的B细胞中Erk信号传导的降低将对抗体应答的各种元件具有相反的作用，所述抗体应答的各种元件对DGKz缺失的作用具有相反的作用（具体目标2）;并将使用Erk 1和Erk 2的一些但不是全部等位基因的缺失与DGKz缺失的组合来遗传地测试以下假设：B细胞中的DGKz缺陷由Erk信号传导的升高而不是其他可能的信号传导效应引起（具体目标3）。这三个目标将共同检验DGKz在成熟B细胞中主要通过调节Erk水平起作用的假设 信号传导以提供对B细胞活化、扩增的亲和力辨别，特别是用于控制早期浆细胞的数量，并且另外将解决这种调节的生物学重要性。

DESCRIPTION (provided by applicant): Signaling by the B cell antigen receptor (BCR) is induced by antigen engagement and is regulated in both quantitative and qualitative ways by dynamic alterations in the levels or activities of key negative regulatory molecules. We hypothesize that such regulation is critical for providing optimal control of antibody responses to limit autoreactivity and to promote production of high quality antibodies. Among the prominent signaling pathways activated by the BCR is activation of phospholipase Cg2, which generates the second messengers diacylglycerol (DG) and inositol trisphosphate. The proposed studies focus on regulation of DG levels in the membrane by the diacylglycerol kinases (DGKs). We have found that DGKa and DGKz, which appear to be the two principle forms of this negative regulator in lymphocytes, are upregulated as B cells mature in the spleen and are downregulated soon after antigen-induced activation of mature B cells. These and other observations suggest that dynamic regulation of DGKs plays an important role in regulation of B cell activation thresholds. We have characterized the effect of ablation of DGKa or DGKz on DG signaling in mature B cells and find that DGKz is the key regulator, while DGKa plays a secondary role. In response to a T cell-independent type 2 antigen, DGKz-/- mice make greater and faster antibody responses. Moreover, the responses of DGKz-/- B cells to a T cell-dependent antigen are also increased, especially with regard to the generation of early extrafollicular plasma cells. These studies suggest that the amount of BCR-induced DG signaling provides affinity discrimination for the early plasma cell response. The proposed studies will determine the biological significance of attenuation of DG signaling by DGKz in B cells for host defense to influenza virus infection (Specific Aim 1); will test the hypothesis that decreases in Erk signaling in B cells resulting from deletion of some but not all alleles of Erk1 and Erk2 in an allelic series will have the opposite effect on various elements of the antibody response to the effect of deletion of DGKz (Specific Aim 2); and will use deletion of some but not all alleles of Erk1 and Erk2 in combination with DGKz deletion to genetically test the hypothesis that the major effects of DGKz-deficiency in B cells result from elevation of Erk signaling and not other possible signaling effects (Specific Aim 3). Together these three aims will test the hypothesis that DGKz in mature B cells acts primarily via modulating the level of Erk signaling to provide affinity discrimination for B cell activation, expansion, and especially for controlling the numbers of early plasma cells, and in addition will address the biological importance of this regulation.