New perspective on innate antibodies in mice

描述（由申请人提供）：目前对细菌刺激（如脂多糖）的先天免疫反应的概念（例如，这里使用的鼠伤寒沙门氏菌的LPS）主要基于对未刺激小鼠脾细胞的体外刺激的数据。然而，我们最近在体内小鼠模型中使用LPS刺激的研究结果表明，许多体外数据不适合模拟体内必然发生的先天反应。同样，我们的发现也提出了一个问题，即如何将体内模型（b细胞转基因、TLR-缺陷、寄生虫感染等）的数据与正常（基因完整）动物的LPS反应联系起来。具体来说，我们发现体内大部分LPS刺激的浆细胞反应是由B-1a （CD5+ B-1）细胞产生的，其中大部分细胞在注射LPS后才迁移到脾脏。此外，我们发现体内对LPS的直接反应是由脾脏中的B-1a细胞产生的，它们在1-2天内分化为浆细胞，而不进行细胞分裂。浆细胞分化的初始波在体内总体反应中所占比例相对较小，在第3天达到峰值，主要由迁移的B-1a细胞在分化为浆细胞之前（或同时）分裂产生。然而，早期应答者的快速反应能力，可以比作原始免疫记忆，可能是利用先天免疫系统“填补空白”直到适应性免疫系统接管的能力的关键。这里提出的研究旨在提供一个清晰的观点，B细胞和机制参与先天抗体应答入侵的病原体，包括但不限于LPS。迄今为止，我们的研究结果表明，我们可以有效地利用介导这些反应的微小功能性B细胞亚群（分别占未刺激或lps刺激小鼠脾脏细胞的0.1-3%）。因此，我们现在建议进一步定义区分常驻B-1细胞和移民B-1细胞反应的细胞、解剖和分子机制，并确定其他B细胞区室和受体相互作用对先天反应的贡献程度。总之，这些研究将为开发复杂的先天免疫机制提供一个全面和信息丰富的模型，该模型涉及必须迅速产生的天然抗体反应，以尽量减少入侵病原体造成的损害。公共卫生相关性：这里提出的研究旨在为参与入侵病原体的先天抗体反应的B细胞和机制提供清晰的观点。迄今为止，我们的研究结果表明，我们可以有效地利用介导这些反应的微小功能性B细胞亚群。这些研究将为建立一个全面和信息丰富的模型提供基础，该模型涉及必须迅速产生的天然抗体反应，以尽量减少入侵病原体造成的损害。

DESCRIPTION (provided by applicant): Current concepts of innate immune responses to bacterial stimuli such as lipopolysaccharides (e.g., the LPS from S. typhimurium used here) are largely based on data from in vitro stimulation of spleen cells taken from unstimulated mice. However, our recent findings with LPS stimulation in an in vivo mouse model demonstrate that much of this in vitro data is not suitable for modeling innate responses, which occur perforce in vivo. Similarly, our findings raise questions about the how to relate data from in vivo models (B-cell transgenic, TLR- deficient, parasite infection, etc.) to LPS responses in normal (genetically intact) animals. Specifically, we find that the majority of the LPS-stimulated plasma cell response in vivo is produced by B-1a (CD5+ B-1) cells, most of which only migrate into the spleen after LPS injected. Further, we find that the immediate response to LPS in vivo is produced by the B-1a cells that are resident in the spleen and surprisingly differentiate into plasma cells within 1-2 days without undergoing cell division. This initial wave of plasma cell differentiation accounts for a relatively small proportion of the overall in vivo response, which peaks at day 3 and is largely produced by immigrant B-1a cells that divide before (or while) differentiating to plasma cells. However, the rapid response capabilities of the early responders, which can be likened to primitive immunologic memory, may be key to the ability to use the innate immune system to "fill in the gap" until the adaptive immune system can take over. Studies proposed here are designed to provide a clear view of the B cells and mechanisms that participate in innate antibody responses to invading pathogens, including but not restricted to LPS. Our findings to date demonstrate that we can work effectively with the tiny functional B cell subsets that mediate these responses (0.1-3% of spleen cells from unstimulated or LPS-stimulated mice, respectively). Thus, we now propose to further define the cellular, anatomical and molecular mechanisms that distinguish resident B-1 responses from those of immigrant B-1 cells, and to determine the extent to which other B cell compartments and receptor interactions contribute to the innate response. Together, these studies will provide grounds for developing a comprehensive and informative model of the complex innate immunity mechanisms involved in natural antibody responses that must be produced rapidly to minimize damage due to invading pathogens. Public Health Relevance: Studies proposed here are designed to provide a clear view of the B cells and mechanisms that participate in innate antibody responses to invading pathogens. Our findings to date demonstrate that we can work effectively with the tiny functional B cell subsets that mediate these responses. These studies will provide grounds for developing a comprehensive and informative model of the complex innate immunity mechanisms involved in natural antibody responses that must be produced rapidly to minimize damage due to invading pathogens.