Selective Presentation of Autoantigens by B Cells

描述(申请人提供)：在目前的申请中，我们测试了一种假设，即B细胞的MHC II类限制性抗原递呈是免疫耐受自身抗原崩溃的关键诱发事件，特别是那些导致自身免疫性糖尿病的免疫耐受。这一假说的一个关键组成部分将在我们的实验中得到验证，即许多启动或传播自身免疫的多肽与MHC II类分子的相互作用稳定性较低。这些与第II类分子的低稳定性相互作用使这些多肽在内体将多肽装载到第II类细胞中时对“DM编辑”特别敏感，从而诱导中枢耐受。因此，DM编辑排除了这些复合体在胸腺抗原提呈细胞(APC)上的表达。由于DM的编辑，对这些低稳定性多肽的自我反应T细胞在T细胞发育过程中不会被删除。我们假设，在外周，B细胞通过MHC编码的DO分子的B细胞特异性表达，具有选择性地呈递这些与MHC-II类分子相关的低稳定性自体多肽的能力。DO的表达将减弱DM对APC内体隔室内这些多肽的编辑，允许它们在细胞表面从头表达。对上述假设的检验将通过推导出一种将与IDDM有关的自体多肽靶向于抗原特异性B细胞的通用策略来完成。我们预计，由于减弱的DM编辑，B细胞将增强其呈递这些低稳定性、隐蔽的自体肽的能力，并且它们呈递这些抗原的能力将打破体内的耐受性。这笔赠款的目标将通过4个具体目标来实现：具体目标1.获得针对抗原特异性B细胞的自体抗原T细胞表位的分子结构。特定目的2.测定多肽的运动稳定性：与自身免疫有关的II类复合体。特定目的3.检测抗原特异性B细胞是否表现出增强的提呈自身抗原性多肽的能力。具体目的4.检测体内B细胞抗原提呈对打破自身抗原耐受的影响。

DESCRIPTION (provided by applicant): In the current application, we test the hypothesis that MHC class II-restricted antigen presentation by B cells is a critical precipitating event in the breakdown of immunological tolerance to self antigens, in particular those that are responsible for autoimmune diabetes. One key component of this hypothesis that will be tested in our experiments is that many of the peptides that initiate or propagate autoimmunity have low stability interactions with MHC class II molecules. These low stability-interactions with class II makes these peptides exceptionally sensitive to "DM editing" during endosomal loading of peptides onto class II within cells that induce central tolerance. DM editing thus precludes expression of these complexes on thymic antigen presenting cells (APC). Because of DM editing, self-reactive T cells to these low stability peptides are not deleted during T cell development. We hypothesize that in the periphery, B cells possess a selective ability to present these low stability self-peptides in association with MHC-class II molecules by virtue of B cell specific expression of the MHC-encoded DO molecule. DO expression will attenuate DM editing of these peptides within endosomal compartments of APC, allowing their de novo expression at the cell surface. Testing of the above hypothesis will be accomplished by deriving a generalized strategy for targeting of the self peptides implicated in IDDM to antigen-specific B cells. We expect that because of attenuated DM editing, B cells will be potentiated in their ability to present these low stability, cryptic self peptides and their presentation of these antigens will break tolerance in vivo. The goals of this grant will be accomplished through 4 Specific Aims: Specific Aim 1. Derive a molecular construct that targets autoantigenic T cell epitopes to antigen-specific B cells. Specific Aim 2. Determine the kinetic stability of peptides: class II complexes that are implicated in autoimmunity. Specific Aim 3. Test whether antigen-specific B cells display potentiated ability to present autoantigenic self peptides. Specific Aim 4. Test the effect of B cell antigen presentation in vivo on breaking of self tolerance to autoantigens.