Maintaining B cell immunity with aged B lymphocytes

描述（由申请人提供）：B细胞为我们提供针对多种感染性微生物的抗体。在人的一生中，B细胞在骨髓中产生，这一过程被称为B淋巴生成。即便如此，在人类中，B细胞免疫力随着年龄的增长而下降，使老年人更容易受到感染和自身免疫性疾病的影响，对疫苗接种的反应也更弱。在家兔中，B淋巴生成只在出生后的几周内发生，然而，它们一生都保持着强大的B细胞免疫力。在本次资助中，我们将研究兔B淋巴生成发育终止的机制；肠道相关淋巴组织（GALT）是否有助于维持兔一生中B细胞的稳态，在没有持续的B淋巴生成的情况下；以及如何重新启动B淋巴系统。在目标1中，我们将通过体外培养和假定的淋巴细胞祖细胞的过继转移来识别和表征骨髓中B淋巴生成被阻止的分化阶段。在Aim 2中，我们将通过掺入BrdU来确定GALT中B细胞的周转率，并确定GALT B细胞向其他外周淋巴组织转移的速度。此外，我们将评估GALT对维持B细胞免疫的贡献，通过手术切除成年兔子体内所有有组织的GALT，并首次在任何物种中进行测试，以确定GALT是否在整个生命过程中作为其他淋巴组织的B细胞储存库。在Aim 3中，我们将使用抗体和诱饵可溶性受体或细胞外基质分子的体内表达来测试三种候选分子（激活的Notch-1、IL-7的剪接变体或细胞外基质蛋白）中的一种或多种是否具有重新启动B淋巴生成的能力。这些实验的数据将有助于了解B淋巴生成下降的机制，以及在没有B细胞新生发育的情况下如何维持B细胞免疫。这些结果为在老年人B细胞免疫力下降时维持强健的免疫反应提供了潜在的解决方案。这项资助计划的研究意义重大，因为到2030年，20%的美国人口预计将达到65岁或以上，并且B细胞免疫系统减弱。这项工作有可能确定治疗干预的目标，使老年人保持健康的免疫系统。

DESCRIPTION (provided by applicant): B cells provide us with antibodies against a multitude of infectious microorganisms. In humans, B cells are produced in the bone marrow throughout life in a process called B lymphopoiesis. Even so, in human, B cell immunity declines with age leaving the elderly more susceptible to infections and autoimmune diseases, and less responsive to vaccinations. In rabbits, B lymphopoiesis occurs for only a few weeks after birth, and yet, they maintain robust B cell immunity throughout life. In this grant, we will study the mechanism by which B lymphopoiesis is developmentally-terminated in rabbits; whether gut-associated lymphoid tissues (GALT) contribute to maintenance of B cell homeostasis throughout the rabbit's life in the absence of ongoing B lymphopoiesis; and how B lymphopoiesis can be reinitiated. In Aim 1, we will identify and characterize the stage of differentiation at which B lymphopoiesis is arrested in bone marrow by using in vitro cultures and adoptive transfer of putative lymphocyte progenitors. In Aim 2, we will determine the turnover rate of B cells in GALT by incorporation of BrdU, and determine the rate at which GALT B cells seed other peripheral lymphoid tissues. Further, we will assess the contribution of GALT to maintenance of B cell immunity by surgically removing all organized GALT from adult rabbits and testing for the first time in any species, whether GALT serves as a reservoir of B cells for other lymphoid tissues throughout life. In Aim 3, we will use antibodies and in vivo expression of decoy soluble receptors or extracellular matrix molecules to test if one or more of three candidate molecules, activated Notch-1, a splice variant of IL-7, or an extracellular matrix protein, has the capacity to reinitiate B lymphopoiesis. Data from these experiments will provide an understanding of the mechanism by which B lymphopoiesis declines, and how B cell immunity can be maintained in the absence of de novo development of B cells. These results should provide potential solutions for maintaining robust immune responses in the elderly as B cell immunity declines. The research proposed in this grant is significant because by the year 2030, 20% of the US population is expected to be age 65 or older and have diminished B cell immune systems. This work has the potential to identify targets for therapeutic interventions that will allow the elderly to maintain a healthy immune system.