MOLECULAR CHANGES IN ANTIBODY AFFINITY IN THE ELDERLY

描述（改编自申请人的摘要）： 这项建议是研究能力下降的分子基础， 在许多老年人的免疫系统中， 亲和抗体，从而产生有效的免疫应答， 疫苗或感染。 为了实现这一目标，校长 研究者将研究与年龄相关的关系变化 免疫球蛋白VH和VL基因的结构和功能之间的关系， 产生天然抗Gal抗体。抗Gal占1% 在人体内循环IgG，并与 碳水化合物结构Gala 1 - 3GalB 1 -4GlcNAc-R（称为α-半乳糖基 表位）。 多达1%的循环B淋巴细胞可以产生抗- 加 本申请人已经发现，大多数测序的Vh基因在大肠杆菌中表达。 产生抗Gal的淋巴样克隆，聚集在 VH 3免疫球蛋白基因家族，并且这些基因经历体细胞免疫， 突变。 抗半乳糖苷酶活性的增龄性变化分析 已经证明在许多老年人中这种抗体的亲和力丧失 个体首席研究员建议研究两种可能的 可能导致抗Gal抗体年龄相关性损伤的机制 1）VH和VL基因的不同利用 抗-Gal合成的库;和2）受损的亲和力成熟 由于年龄相关的体细胞变化， 突变过程 为此，他将构建组合 在年轻和老年个体中噬菌体展示文库以及分离物 展示抗半乳糖的噬菌体。 抗Gal VH的比较分析 和VL基因库在年轻人和老年人，并确定 由此产生的抗体亲和力，将使申请人能够建立 年龄相关的抗体亲和力降低是否与 用于抗半乳糖苷合成的基因库。 比较V 具有相应生殖系基因的基因序列将允许 研究人员确定与年龄相关的变化是否反映了 抗Gal产生基因中体细胞突变的过量或缺乏。 的 申请人将进一步确定老年人是否有低 亲和血清抗Gal保留了一些高亲和力的克隆，通过选择 高亲和力抗Gal噬菌体。 最后，通过将抗Gal亲和力与对免疫缺陷病毒的免疫应答相关联， 流感病毒疫苗，主要研究者将确定 抗半乳糖胺抗体是否可以预测免疫系统在 老年人产生高亲和力抗体。 因此，由 利用抗Gal系统，申请人旨在了解 与年龄相关的损伤的分子基础 人类的体液免疫反应。

DESCRIPTION (Adapted from the Applicant's Abstract): The objective of this proposal is to study the molecular basis for the decreased ability of the immune system in many elderly individuals, to produce high affinity antibodies and thus mount an effective immune response to vaccines or infections. To pursue this objective, the principal investigator will study the age-associated changes in the relationship between structure and function of immunoglobulin VH and VL genes which produce the natural anti-Gal antibody. Anti-Gal constitutes 1% of circulating IgG in humans and interacts specifically with the carbohydrate structure Gala1-3GalB1-4GlcNAc-R (termed alpha-galactosyl epitope). As many as 1% of circulating B lymphocytes can produce anti- Gal. The applicant has found that most of the sequenced VH genes in anti-Gal producing lymphoid clones, cluster within a distinct region of the VH3 immunoglobulin gene family, and that these genes undergo somatic mutations. Analysis of age-associated changes in activity of anti-Gal have demonstrated loss of affinity of this antibody in many elderly individuals. The principal investigator proposes to study two possible mechanisms which may cause the age-associated impairment in anti-Gal affinity in humans: 1) different utilization of VH and VL genes repertoire for anti-Gal synthesis; and 2) impaired affinity maturation in anti-Gal genes because of age-associated changes in the somatic mutations process. For this purpose he will construct combinatorial phage display libraries in young and in elderly individuals and isolate the anti-Gal displaying phage. Comparative analysis of the anti-Gal VH and VL gene repertoire in the young and elderly, and determination of the resulting antibody affinities, will enable the applicant to establish whether the age-associated decrease in antibody affinity correlates with the gene repertoire used for anti-Gal synthesis. Comparison of the V gene sequences with the corresponding germline genes will allow the investigators to establish whether the age-associated changes reflect the excess or paucity of somatic mutations in anti-Gal producing genes. The applicant will further determine whether elderly individuals with low affinity serum anti-Gal retain some high affinity clones, by selecting high affinity anti-Gal phage from the libraries of these individuals. Lastly, by correlating anti-Gal affinity with the immune response to an influenza virus vaccine, the principal investigator will determine whether anti-Gal can predict the competence of the immune system in elderly individuals to produce high affinity antibodies. Thus, by exploiting the anti-Gal system, the applicant aims to understand the molecular basis of the well-documented age-associated impairment of humoral immune responses in humans.