Implications of B10-like cell expansion in a model of impaired receptor editing

项目概要/摘要 虽然B细胞最为人所知的是通过产生抗原特异性的免疫球蛋白来提供体液免疫。 越来越多的证据表明，一些B细胞亚群可以起到负调节作用， 通过产生免疫抑制性细胞因子IL 10来抑制炎症反应。也许最好的特点是 这些亚群中的一种是B10 B细胞，其独特之处在于其CD 5 + CD 1dhiCD 19 hi表型和表达能力。 响应促有丝分裂刺激而分泌IL 10。B10 B细胞被认为促进抗原特异性抑制 通过由同源B细胞-T细胞建立的IL 10（B细胞）-IL 21（T细胞）反馈环， 细胞相互作用有趣的是，一些CD 5 + B细胞群体倾向于与膜-细胞反应。 相关的自身抗原，并且还可以产生IL 10样B10 B细胞。此外，某些疾病 与CD 5 + B细胞扩增相关的白血病，如慢性淋巴细胞白血病和干燥综合征，显示 当抗体攻击宿主自身细胞时，自身免疫性血细胞减少症的发病率增加。 总之，这些数据提高了IL 10依赖性反馈机制可能在 逆转以帮助限制对膜抗原反应B细胞，以及该调节环的破坏 可能导致B细胞固有的自身免疫表现。我们以前生产的转基因小鼠（称为 dnRAG 1小鼠），其表现出用于改变B细胞受体特异性远离自身受体的受体编辑缺陷。 反应性这些动物显示出扩增的CD 5 + B细胞群和受损的抗体产生。我们 已经发现dnRAG 1 CD 5 + B细胞共享B10 B细胞的免疫表型和IL 10-能力， 导致我们假设，未能成功编辑针对某些自身免疫缺陷的B细胞受体特异性， 抗原可导致B细胞获得B10样特性以抑制B细胞内在自身免疫。 与这一假设相一致，我们在这里表明，在dnRAG 1小鼠中IL 10缺乏导致IgM升高 生产将通过分析野生型和dnRAG 1小鼠对IL 10 +/+和IL 12 +/+的耐受性来进一步检验这一假设。 IL 10-/-背景，以比较自发和刺激诱导的抗体水平、自身抗原反应性 谱、免疫球蛋白可变基因使用模式和IgM抗体产生细胞的频率。我们 还将确定是否将来自IL 10 +/+ dnRAG 1小鼠的CD 5 + B细胞过继转移到IL 10-/-dnRAG 1中 小鼠可以恢复这些动物的免疫抑制。此外，我们将测试受损的受体是否 在表达定点磷脂酰胆碱（PtC）特异性重链转基因的小鼠中进行编辑， CD 5 + B细胞积累和IL 10能力，并抑制总的或PtC特异性IgM产生。的 本研究的结果可能揭示了B细胞-内源性自身免疫 对某些自身抗原的免疫抑制，并将识别可能受到耐受的自身抗原。 通过受体编辑诱导。这项工作也可能提示某些自身免疫表现的病因， 如血细胞减少症，这可能是与CD 5 + B细胞扩增相关的疾病的临床并发症。

PROJECT SUMMARY/ABSTRACT Although B cells are best known for providing humoral immunity through the production of antigen-specific antibodies, accumulating evidence suggests some B cell subsets can function to negatively regulate inflammatory responses by producing the immunosuppressive cytokine IL10. Perhaps the best characterized of these subsets is the B10 B cell, which is distinctive for its CD5+CD1dhiCD19hi phenotype and ability to secrete IL10 in response to mitogenic stimuli. B10 B cells are thought to promote antigen-specific suppression of autoreactive T cells through an IL10 (B cell) – IL21 (T cell) feedback loop established by cognate B cell-T cell interactions. Interestingly, some CD5+ B cell populations have a propensity to react with membrane- associated self-antigens and may also produce IL10 like B10 B cells. Furthermore, certain diseases associated with expanded CD5+ B cells, such as chronic lymphocytic leukemia and Sjögren’s syndrome, show an increased incidence of autoimmune cytopenias that occur when antibodies attack the host’s own cells. Together, these data raise the possibility that the IL10-dependent feedback mechanism may function in reverse to help constrain B cells reactive to membrane antigens, and that breakdown of this regulatory loop may cause B cell-intrinsic autoimmune manifestations. We previously generated transgenic mice (called dnRAG1 mice) which exhibit a receptor editing defect used to alter B cell receptor specificity away from self- reactivity. These animals show an expanded CD5+ B cell population and impaired antibody production. We have found that dnRAG1 CD5+ B cells share the immunophenotype and IL10-competence of B10 B cells, leading us to hypothesize that a failure to successfully edit B cell receptor specificity against certain self- antigens may cause the B cell to acquire B10-like properties to suppress B cell-intrinsic autoimmunity. Consistent with this hypothesis, we show here that IL10-deficiency in dnRAG1 mice leads to elevated IgM production. This hypothesis will be further tested by analyzing wild-type and dnRAG1 mice on IL10+/+ and IL10-/- backgrounds to compare spontaneous and stimulation-induced antibody levels, autoantigen reactivity profiles, immunoglobulin variable gene usage patterns, and the frequency of IgM antibody-producing cells. We will also determine whether adoptively transferring CD5+ B cells from IL10+/+ dnRAG1 mice into IL10-/- dnRAG1 mice can restore immune suppression in these animals. Furthermore, we will test whether impaired receptor editing in mice expressing a site-directed phosphatidylcholine (PtC)-specific heavy chain transgene enhances CD5+ B cell accumulation and IL10-competence, and suppresses total or PtC-specific IgM production. The results obtained from this study may reveal an important new mechanism for how B cell-intrinsic autoimmunity against certain self-antigens are suppressed, and will identify autoantigens that may be subjected to tolerance induction by receptor editing. This work may also suggest an etiology for certain autoimmune manifestations, like cytopenias, that can arise as a clinical complication in diseases associated with expanded CD5+ B cells.