Human B Cell Development and Function in Humanized Mice Expressing Human BAFF

描述(由申请人提供)：造血人源化小鼠(HU-小鼠)已经被开发出来，用于在体内实验模型中研究人类免疫系统。这些小鼠携带着人类免疫系统，可以通过与小鼠身上使用的方法类似的方法进行操作。因此，HU-小鼠可以作为一个有效的翻译系统来研究在小鼠免疫系统中的观察结果是否适用于人类，并探索人类繁殖的免疫反应的自然变异。然而，尽管最近在建立这种动物模型方面取得了进展，人-鼠还没有为人类免疫系统提供一个最佳的环境。关于B细胞，目前的Hu-小鼠模型不支持高效和长期的成熟B细胞的产生和/或维持，限制了该模型在需要成熟B细胞功能的研究中的有效性。无论是在小鼠体内还是在人类体内，BAFF都是一种重要的B细胞动态平衡因子。除了维持成熟B细胞的存活外，BAFF还促进Ig类转换，从而促进体液反应。最近的研究表明，在HU-小鼠体内，成熟B细胞的低效率存活可能部分是由于缺乏人的BAFF。为了支持这些观察，我们发现人BAFF的增加与HU-小鼠中更多的人成熟B细胞有关，但这种人细胞因子的表达只有在这些动物嵌合体中的一些和较晚的时间点才能检测到。在这里，我们建议用一种新型的小鼠品系来代替小鼠的BAFF，以表达人的BAFF。我们的假设是，表达内源性人BAFF的HU小鼠将支持更快和更多的成熟B细胞的产生，并促进更好的质量和数量的抗体应答。为了实现这些目标，我们将发展以下两个目标：1)产生人BAFF基因敲除小鼠；2)在人类BAFF基因敲入HU小鼠中鉴定成熟B细胞的发育和功能。这些研究旨在增加HU-小鼠作为实验动物模型的相关性，以研究人类免疫系统，更具体地说，B细胞和体液反应。本工作的创新之处在于建立了人BAFF基因敲入小鼠品系，并对表达人BAFF基因的人B细胞群在HU小鼠体内的发育进行了表征。我们的假设是，人BAFF基因敲入的HU-小鼠将表现出更多的人类成熟B细胞群和更高的抗原特异性抗体应答，改进了该模型，用于研究人类抗体应答和B细胞生物学。

DESCRIPTION (provided by applicant): Hematopoietic humanized mice (hu-mice) have been developed to study the human immune system in an experimental in vivo model. These mice bear a human immune system that can be manipulated with methodologies similar to those utilized in mice. Hu-mice, therefore, can be used as an effective translational system to investigate whether observations made in the mouse immune system hold true in the human, and to explore the natural variation of outbred human immune responses. Despite recent advances in the establishment of this animal model, however, hu-mice do not yet provide an optimal environment to the human immune system. With regard to B cells, the current hu-mouse model does not support efficient and prolonged generation and/or maintenance of mature B cells limiting the validity of this model in studies that require mature B cell functions. BAFF isan important homeostatic factor for B cells both in mice and in humans. In addition to sustaining the survival of mature B cells, BAFF also promotes Ig class switch and, therefore humoral responses. Recent studies have suggested that the inefficient survival of mature B cell in hu-mice might be in part due to the absence of human BAFF. In support of these observations, we have found that increased production of human BAFF correlates with higher numbers of human mature B cells in hu-mice, but that expression of this human cytokine becomes detectable only in some of these animal chimeras and at late time points. Here we propose to genetically engineer a novel mouse strain that expresses human BAFF in place of mouse BAFF. Our hypothesis is that hu-mice expressing endogenous human BAFF will support faster and increased generation of mature human B cells and promote antibody responses of better quality and magnitude. To achieve these goals, we will develop the following two aims: 1) to generate human BAFF knock- in mice; and 2) to characterize the development and function of mature B cells in human BAFF knock-in hu- mice. These studies aim at increasing the relevance of hu-mice as experimental animal models for the investigation of the human immune system and, more specifically, of B cell and humoral responses. The innovation of this work lies in the generation of the human BAFF knock-in mouse strain and in the characterization of the human B cell population developing in hu-mice that express human BAFF. Our hypothesis is that human BAFF knock-in hu-mice will display a larger human mature B cell population and heightened antigen-specific antibody responses, improving this model for studies of human antibody responses and B cell biology.