BIOCHEMICAL & MOLECULAR EVENTS OF B CELL ACTIVATION BY POLYSACCHARIDES

生化

• 批准号: 6161344
• 负责人: K A BRORSON
• 金额: --
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6161344
• 关键词: B lymphocyte; antibacterial antibody; antigen antibody reaction; bacterial polysaccharides; bacterial vaccines; cell cycle; crosslink; cyclins; enzyme activity; gene expression; gene induction /repression; gene mutation; genetically modified animals; laboratory mouse; leukocyte activation /transformation; messenger RNA; protein tyrosine kinase; tissue /cell culture

Immunity to many encapsulated bacterial pathogens involves antibody responses by B cells activated by capsular polysaccharides via surface Ig receptors. B cells activated by Ig cross-linking undergo an ordered chain of events. These events include stimulation of kinase activity, gene and nuclear factor activation, and entry into cell cycle. Mice with the x-linked immunodeficiency gene (xid) possess a mutation in the pleckstrin homology domain of Bruton's tyrosine kinase (Btk). These animals are unresponsive to polysaccharide antigens. Moreover their B cells do not proliferate after Ig cross-linking, although they do enlarge. To determine at which point in the activation pathway xid cells become arrested, both early and late events are being compared in sIg activated xid and wildtype B cells. We have found that early G1 events, such as nuclear factor and proto-oncogene induction occur in xid cells normally. Furthermore, the activity of src related kinases was intact in xid cells. However, induction of cyclin proteins did not occur in xid cells. Their absence correlated with an absence of cyclin mRNA, arguing that nuclear events associated with normal cyclin gene induction are blocked in xid. The cyclin inhibitor p27kip1 was modulated normally in sIg actiavted B cells. Further studies now underway include the construction of Btk-GST fusion proteins to examine Btk functional differences between xid and wild type B cells. These fusion constructs are being used to probe for pleckstrin homology domain binding substrates to determine how the 28R->C xid mutation ablates Btk function. Also, xid-myc transgenic mice have been bred to produce xid B cell lines. A clear understanding of the events associated with sIg mediated activation is required to optimize immune responses to polysaccharide vaccines because these antigens have the ability to trigger B cells directly. Because of their defect, xid mice can be used experimentally to isolate the function of anti-polysaccharide antibodies from other protectiv mechanisms against encapsulated pathogens. This understanding is especially important for vaccination of very young and elderly populations which respond poorly to polysaccharides.

对许多被包裹的细菌病原体的免疫涉及抗体 荚膜多糖通过表面IG激活B细胞的反应 受体。 由IG交联激活的B细胞经历有序链 事件。 这些事件包括刺激激酶活性、基因和 核因子激活，进入细胞周期。 只小鼠体内注射 X连锁免疫缺陷基因（XID）在pleckstrin中具有突变 布鲁顿酪氨酸激酶（Btk）同源结构域。 这些动物是 对多糖抗原无反应。 此外，他们的B细胞不会 在IG交联后增殖，尽管它们确实放大。 到 确定XID细胞在活化途径中的哪个点变成 被捕，无论是早期和晚期事件正在进行比较，在sIg激活 xid和野生型B细胞。 我们发现，早期的G1事件，如 核因子和原癌基因诱导通常发生在XID细胞中。 此外，src相关激酶的活性在xid细胞中是完整的。 然而，诱导细胞周期蛋白没有发生在xid细胞。 他们的 缺乏与细胞周期蛋白mRNA的缺乏相关，认为细胞核 与正常细胞周期蛋白基因诱导相关的事件在XID中被阻断。 在sIg激活的B中，细胞周期蛋白抑制剂p27 kip 1被正常调节 细胞 目前正在进行的进一步研究包括构建Btk-GST 融合蛋白，以检查xid和野生型之间的Btk功能差异 B型细胞。 这些融合结构被用来探测 pleckstrin同源结构域结合底物，以确定28 R->C xid突变消除了Btk功能。 此外，xid-myc转基因小鼠具有 已经培育出xid B细胞系。 清楚了解 需要与sIg介导的激活相关的事件来优化 多糖疫苗的免疫应答，因为这些抗原具有 直接触发B细胞的能力。 由于他们的缺陷，xid 小鼠可以实验性地用于分离 来自其他保护机制的抗多糖抗体 包囊病原体。 这一认识对于 接种反应较差的非常年轻和老年人群， 多糖