Maturation of the Anitbody Response to a Protein Antigen

抗体对蛋白质抗原反应的成熟

• 批准号: 9630412
• 负责人: Ronald Jemmerson
• 金额: $ 30万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-08-01 至 2000-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9630412&HistoricalAwards=false
• 关键词: Maturation; Anitbody; Response; Protein; Antigen

9630412 Jemmerson Following exposure of the immune system of experimental animals such as mice to small chemical compounds, the antibodies that are produced initially by the white cells bind the compounds weakly, then after about one week, the antibodies that are made begin to bind the compounds more strongly until a maximum binding ability is achieved. This increased strength in binding, also known as affinity, results from changes, or mutations, in the genes that code for the antibodies. Although not yet definitively shown, it is believed that this model also applies to the immune response to more complex molecules including proteins which are present on microorganisms that the immune system normally eliminates. In this study, this model will be extended to the immune response to a protein that has been well-characterized both structurally and chemically, cytochrome c. In preliminary work it has been determined that several mutations in the genes encoding antibodies specific for cytochrome c do occur after immunizing mice with the protein and that together these mutants result in higher affinity antibody binding. Now, the effect of each of the mutations in the antibody genes on the affinity will be tested by altering the genes at each of the several sites independently. In addition, the structure of a complex of an antibody bound to the protein will be determined using the technique of X-ray crystallography to find out whether the mutations cause changes in the antibodies that directly contact the target molecule (antigen) or whether the effects are indirect. The cytochrome c to be employed in this study is a protein expressed in mice. Previously it was found that the antibody genes used in the immune response to this self antigen are also used in response to a related protein and that during the response the antibodies acquire higher affinity for this protein than for the self antigen. In this study, the mutations in the antibody genes that allo w for this conversion will be determined. It has been suggested for a long time that this may be a general mechanism for immunological recognition of foreign antigens but an experimental system to study it has been available. In summary, this study will extend our understanding of affinity maturation in the antibody response from what was previously known in studies of model compounds to a more complex, protein antigen. It will also provide further insight into how immune recognition of foreign antigens may initiate with the response of antibody-producing white blood cells that possibly evolved to recognize self antigens. ***

小行星9630412 在实验动物如小鼠的免疫系统暴露于小化合物之后，最初由白色细胞产生的抗体与化合物的结合较弱，然后在约一周后，所产生的抗体开始与化合物的结合更强，直到达到最大结合能力。 这种结合强度的增加，也称为亲和力，是由编码抗体的基因的变化或突变引起的。 尽管尚未明确显示，但据信该模型也适用于对更复杂分子的免疫应答，包括存在于免疫系统通常消除的微生物上的蛋白质。 在这项研究中，该模型将扩展到免疫反应的蛋白质，已被充分表征的结构和化学，细胞色素c。 在初步工作中，已经确定，在用蛋白质免疫小鼠后，编码细胞色素c特异性抗体的基因中确实发生了几个突变，并且这些突变体一起导致更高亲和力的抗体结合。 现在，抗体基因中每个突变对亲和力的影响将通过独立改变几个位点中每个位点的基因来测试。 此外，将使用X射线晶体学技术确定与蛋白质结合的抗体复合物的结构，以确定突变是否导致直接接触靶分子（抗原）的抗体发生变化，或者影响是否是间接的。 本研究中使用的细胞色素c是在小鼠中表达的蛋白质。 以前发现，在对这种自身抗原的免疫应答中使用的抗体基因也用于应答相关蛋白质，并且在应答期间，抗体对这种蛋白质的亲和力高于对自身抗原的亲和力。 在本研究中，将确定允许这种转换的抗体基因中的突变。 长期以来，人们一直认为这可能是免疫学识别外源抗原的一般机制，但研究它的实验系统已经存在。 总之，本研究将扩展我们对抗体应答中亲和力成熟的理解，从先前在模型化合物研究中已知的理解扩展到更复杂的蛋白质抗原。 它还将提供进一步的见解，如何免疫识别外来抗原可能会启动抗体产生白色血细胞的反应，可能进化到识别自身抗原。 ***