Role of natural immunity to self apoptotic exosomes in maintaining immune homeostasis

免疫系统区分自我与非自我，保护机体免受外来生物的伤害。为了保证其稳态，多种机制严密调节免疫系统以避免自身免疫性疾病。经典理论认为，健康的免疫系统需要绝对避免自身反应性淋巴细胞克隆，与此相反，已知先天类B细胞的库包含某种程度的自身反应性，并产生天然抗体。一组重要的天然抗体对凋亡细胞表达的凋亡抗原（napabs）具有特异性。这表明，这些nababs可能在促进凋亡细胞的有效非炎症清除中发挥作用，对维持免疫稳态至关重要。然而，调控nababs产生的机制在很大程度上仍未被探索。我们的研究小组首次描述了一种新颖的结构，这种结构与凋亡内皮细胞在Caspase-3激活的下游释放的外泌体相似。这些凋亡外泌体（ApoExo）明显不同于经典的凋亡小体。我们的观察结果表明，B1细胞对ApoExo包装的自身抗原的记忆可以在正常的免疫库中找到，并且ApoExo的输注触发了对凋亡抗原特异性的IgM和IgG抗体的产生。我们假设新发现的囊泡结构凋亡外泌体刺激存在于正常免疫库中的特异性B细胞分泌天然凋亡抗原自身抗体，在凋亡细胞的非炎症清除中起重要作用。我们还假设炎症信号可以调节这些过程。我们的长期目标是描述凋亡外泌体在维持体内平衡的重要基本免疫过程中的功能目的在本研究计划中，我们提出：目的1：表征凋亡外泌体（ApoExo）特异性天然存在的B细胞库及其自身抗体分泌特征；目的2：评估ApoExo衍生的Ig调节凋亡细胞非炎症清除的能力；目的3：为了评估炎症环境如何调节ApoExo免疫反应科学方法本研究计划围绕一系列结构良好的互补描述性和机制目标进行阐述，建议使用广泛的“工具”阵列用于我们的分析。这些包括大量的转基因小鼠品系和表征和分离外泌体、免疫细胞亚群和抗体的最新技术。重要的是，PI和他的合作者团队在外泌体和免疫学方法方面拥有丰富的经验。影响：该研究项目完成后，将对ApoExo对免疫稳态的贡献提供更深入的了解。据我们所知，这个项目是第一个研究这个吸引人的方向的项目。

BACKGROUND The immune system distinguishes the self from the non-self, allowing protection against foreign organisms from damaging the body. To ensure of its homeostasis, multiple mechanisms tightly regulate the immune system to avoid autoimmune disease. In contrast to the classical theory that a healthy immune system requires an absolute avoidance of self-reactive lymphocyte clones, the repertoires of innate-like B cells are known to incorporate some level of autoreactivity, and to produce natural antibodies. A significant set of natural antibodies are specific to apoptotic Antigens (NapoAbs) expressed by apoptotic cells. It is suggested that these NapoAbs may play a role in facilitating effective non-inflammatory clearance of apoptotic cells of importance in maintaining immune homeostasis. However, of the mechanisms that regulate the production of NapoAbs is still largely unexplored. Our group was the first to characterize a novel structure reminiscent of exosomes that are released downstream of Caspase-3 activation by apoptotic endothelial cells. These Apoptotic Exosomes (ApoExo) are strikingly different from classical apoptotic bodies. Our observations suggest that B1 cell memory to autoantigens packaged in ApoExo can be found within the normal immune repertoire and that the infusion of ApoExo triggers the production of IgM and IgG Antibodies specific to Apoptotic antigens. HYPOTHESIS We HYPOTHESIZE that newly identified vesicular structures Apoptotic Exosomes stimulate specific B cells that exist in the normal immune repertoire to secrete Natural Apoptotic Antigens autoantibodies of importance in non-inflammatory clearance of apoptotic cells. We also hypothesize that inflammatory signals can regulate these processes. OUR LONG-TERM OBJECTIVE is to delineate the functions of Apoptotic Exosomes in basic immunological processes of importance in maintaining homeostasis AIMS In this research program we propose: AIM 1: To characterize the repertoire of naturally occurring B cells specific to Apoptotic Exosomes (ApoExo) and their autoantibody secretion signature AIM 2: To evaluate ApoExo derived Ig capacity to modulate Non-Inflammatory clearance of apoptotic cells AIM 3: To evaluate how inflammatory context modulates ApoExo immune responses SCIENTIFIC APPROACH This research program, articulated around a well-structured series of complementary descriptive and mechanistic aims, proposes to use an extensive array of `tools' available for our analyses. These includes substantial number of genetically modified mouse strain and state of the art techniques to characterize and isolate exosome, immune cells subsets and antibodies. Importantly, the PI and his team of collaborators have extensive experience with exosomes and immunological approaches. IMPACT This research program will provide, upon completion, great insight on ApoExo contribution to immune homeostasis. This program is, to our knowledge, the first to investigate this appealing direction.