Co-stimuli for Human Marginal Zone B Cell Activation

描述（申请人提供）：边缘区B细胞参与小鼠SLE样自身免疫，因此可能在人类SLE的诱导中起重要作用。（即C3 dg结合CD 21的水平升高，它们对BAFF的接近性和敏感性，以及它们对来自微生物的Toll样受体（TLR）结合DNA的接近性和可能的敏感性）可以增强MZ B细胞对弱BCR刺激物的应答能力。重要的是，后者表征了自身反应性B细胞与自身抗原（Ag）的相互作用，并且表达细胞内分子的C3 dg包被的凋亡细胞作为表面Ag可能在MZ内普遍存在。该申请的长期目标是阐明MZ环境内的刺激和人MZ B细胞表面受体表达有助于增强MZ内发现的自身反应性B细胞的活化的机制。使用来自人脾脏的分离的IgM + IgD-CD 27 + MZ B细胞和IgM + IgD + CD 27-滤泡（FO）B细胞，我们将：（a）比较IL-4和BAFF在促进MZ和FO B细胞活力和预防BCR触发的细胞凋亡方面的功效，（B）比较MZ和FO B细胞的BAFF和IL-4受体的密度，（c）用一系列亲和力多样的抗BCR：葡聚糖缀合物CD 21结合位点，确定BCR与CD 21：CD 19共刺激复合物的连接（i）在限制BCR接合的条件下增强BAFF依赖性MZ和FO B细胞增殖和（ii）与BAFF和TLR 9结合CpG DNA基序协作增强MZ或FO B细胞分化的程度，（d）探索同型CD 27：CD 7 O相互作用在上述刺激激活后促进MZ B细胞分化中的作用，和（e）检查当用C3 dg-培养时，正常个体MZ中的自身反应性B细胞是否被触发分泌自身抗体。在BAFF和微生物DNA基序的存在下包被的凋亡细胞。上述体外刺激的功能研究应阐明MZ环境中预期的刺激，特别是在微生物感染期间，是否可以在限制BCR接合的条件下协同促进人B细胞的活化。这些见解应建议免疫干预治疗阻断SLE自身反应性B细胞的激活。

DESCRIPTION (provided by applicant): Marginal zone (MZ) B cells have been implicated in SLE-like autoimmunity in mice and thus may be important in the induction of SLE in man. This proposal is based on the hypothesis that several facets of MZ B cells (i.e. heightened levels of C3dg-binding CD21, their proximity and sensitivity to BAFF, and their proximity and possible sensitivity to Toll-like receptor (TLR)-binding DNA from micro-organisms) may augment the capacity of MZ B cells to respond to weak BCR stimuli. Importantly, the latter characterizes the interaction of autoreactive B cells with self antigen (Ag), and C3dg-coated apoptotic cells expressing intracellular molecules as surface Ag are likely prevalent within the MZ. The application's long-term objectives are to illuminate the mechanisms by which stimuli within the MZ environment and human MZ B cell surface receptor expression contribute to the enhanced activation of autoreactive B cells which are found within the MZ. Using isolated lgM+lgD-CD27+ MZ B cells and lgM+lgD+CD27- follicular (FO) B cells from human spleens, we will: (a) compare the efficacy of IL-4 and BAFF at promoting MZ and FO B cell viability and preventing BCR-triggered apoptosis, (b) compare MZ and FO B cells for density of receptors for BAFF and IL-4, (c) with a series of affinity-diverse anti-BCR:dextran conjugates ¿ CD21 binding sites, determine the degree to which BCR ligation with the CD21 :CD19 costimulatory complex (i) augments BAFF-dependent MZ and FO B cell proliferation under conditions of limiting BCR engagement and (ii) collaborates with BAFF and TLR9-binding CpG DNA motifs to enhance MZ or FO B cell differentiation, (d) explore the role of homotypic CD27:CD7O interactions in promoting the differentiation of MZ B cells upon activation by the above stimuli, and (e) examine whether autoreactive B cells in the MZ of normal individuals are triggered to secrete autoantibody when cultured with C3dg-coated apoptotic cells in the presence of BAFF and microbial DNA motifs. The above functional studies with defined in vitro stimuli should elucidate whether stimuli expected in the MZ environment, particularly during microbial infection, can collaborate in promoting the activation of human B cells under conditions of limiting BCR engagement. Such insights should suggest immunologic intervention therapies for blocking the activation of autoreactive B cells in SLE.