Characterization of the MHC Class II Peptide Loading Complex

描述（由申请方提供）：B细胞和CD 4 T细胞之间的相互作用由肽-MHC II类复合物介导，并支持体液免疫应答的全面发展。B细胞是抗原特异性抗原呈递细胞，其中免疫相关抗原加工发生在B细胞受体（BCR）介导的同源抗原的结合和内化之后。该实验室已经确定，BCR介导的抗原加工发生在抗原（Ag）-BCR泛素化之后，并导致具有独特功能和生物化学性质的衍生肽II类复合物（称为“I型”复合物）的表达。驱动该项目的基本假设是，Ag-BCR复合物的加工发生在位于MHC II类富集抗原加工区室中的MHC II类肽加载复合物（PLC）内。为了验证这一假设，我们将扩展我们的新的初步数据，并采取生物化学方法，以进一步确定在B细胞处理通过BCR介导或液相内吞作用内化的抗原的II类PLC的分子组成（目的1）。我们还将利用“FRET显微镜”方法来研究完整B细胞中II类PLC形成的动力学（目的2）。这个项目的总体目标是 该建议是为了更好地理解BCR介导的抗原加工后II类肽加载的分子机制，并确定II类肽加载是否发生在含有抗原肽的专用来源的PLC内（即，Ag-BCR复合物）。 公共卫生相关性：抗原特异性B细胞和CD 4辅助性T细胞之间的相互作用受到B细胞表达的肽-MHC II类复合物的限制。本项目的目标是确定抗原特异性B细胞产生这些关键的肽类II复合物的分子机制。这些信息将有助于设计新的疫苗 增强这些复合物的产生或治疗方案，以在自身免疫的情况下抑制这种机制。

DESCRIPTION (provided by applicant): Interactions between B cells and CD4 T cells are mediated by peptide-MHC class II complexes and support full development of a humoral immune response. B cells are antigen-specific antigen presenting cells, where immunologically relevant antigen processing occurs subsequent to B cell receptor (BCR)-mediated binding and internalization of cognate antigen. This laboratory has established that BCR-mediated antigen processing occurs subsequent to antigen (Ag)-BCR ubiquitination and results in expression of derivative peptide-class II complexes (termed "Type I" complexes) with unique functional and biochemical properties. The underlying hypothesis driving this project is that processing of Ag-BCR complexes occurs within an MHC class II peptide-loading complex (PLC) located in MHC class II enriched antigen processing compartments. To test this hypothesis, we will extend our new preliminary data and take a biochemical approach to further define the molecular composition of the class II PLC in B cells processing antigen internalized either via BCR-mediated or fluid-phase endocytosis (Aim 1). We will also utilize a "FRET microscopy" approach to study the dynamics of class II PLC formation in intact B cells (Aim 2). The overall goal of this proposal is to gain a better understanding of the molecular mechanism of class II peptide loading subsequent to BCR-mediated antigen processing, and to determine if class II peptide loading occurs within a PLC containing a dedicated source of antigenic peptide (i.e., Ag-BCR complexes). PUBLIC HEALTH RELEVANCE: Interactions between antigen specific B cells and CD4 helper T cells are restricted by B cell expressed peptide-MHC class II complexes. The goal of this project is to define the molecular mechanism by which antigen specific B cells generate these critical peptide-class II complexes. This information will be helpful in the design of new vaccines that enhance the production of these complexes or therapeutic protocols to dampen this mechanism in cases of autoimmunity.