乳铁蛋白免疫复合物的固有免疫增敏驯化效应分子机制研究

Lactoferrin (LTF) is an important defense molecule found in body fluids as well as secondary granules of neutrophils in mammals, it is also a target for autoimmune responses in humans. We have recently found that serum levels of immunocomplexes (ICs) between LTF and specific autoantibodies positively correlated with rheumatoid arthritis and systemic lupus erythematosus, and also that LTF-ICs exhibited not only potent stimulatory activities against human monocytes/macrophages but also the ability to induce long-lasting hyperresponsiveness state of the cells. This is in accordance with recent new internationally accepted concepts that (a) trained innate immunity induced by microbial antigens be regarded as direct evidence for “memory of the innate immune system”; and (b) also that superactive ICs play pivotal roles in the pathogenesis of autoimmune diseases. Related scientific questions can therefore be asked: (i) What are the molecular mechanisms for the potent immunostimulatory activies of LTF-IC? (ii) Will LTF-IC play significant pathogenic roles in the development of autoimmune diseases? (iii) Is it possible to develop LTF-IC-specific treatment strategy for related autoimmune disorders? To address the above questions, this project will conduct in vivo and in vitro experiments designed to thoroughly assess our working hypothesis on molecular and cellular levels. The proposed project, well supported by preliminary data, focuses on hotspot of the international immunology forefront, and therefore major advances can be expected.

乳铁蛋白（LTF）是广泛分布于黏膜分泌液、其它体液以及中性粒细胞次级颗粒的固有免疫分子，也是人某些自身免疫反应的靶分子。我们的前期工作发现，血液中LTF与自身抗体形成免疫复合物（LTF-IC）的水平与类风湿性关节炎和系统性红斑狼疮等自身免疫病密切相关，而且LTF-IC对人单核巨噬细胞不仅具有超强刺激活性，还能诱导其进入长时间超敏状态。这与国际免疫学界最近关于免疫增敏驯化导致“固有免疫记忆”以及强活性免疫复合物在自身免疫病致病机理中扮演重要角色的共识不谋而合。LTF-IC发挥超强活性的分子机制如何？与炎性自身免疫病理损伤有怎样的关系？能否通过靶向干预LTF-IC活性而实现相关疾病的免疫治疗？针对上述问题，本项目通过分子生物学、细胞生物学以及体内、外实验对相关假说进行验证与解析。研究内容理论联系实际，与国际研究热点相吻合，有望取得源头创新性成果。

本项目围绕乳铁蛋白免疫复合物（LF-IC）对单核巨噬细胞的训化致敏作用及其在类风湿性关节炎（RA）中的致病机制这一科学问题，从体外细胞水平，RA患者以及小鼠模型三方面进行了探讨。在为期四年的项目执行过程中，我们顺利地完成了研究任务，取得了有价值的研究结果，实现了既定目标，并在此基础上对研究内容做了适当拓展和延伸。我们的主要研究结论是：1）LF-IC通过影响单核巨噬细胞的表观遗传修饰使巨噬细胞处于高敏状态；并且LF-IC驯化的巨噬细胞与RA滑膜巨噬细胞具有高度相似性；2）LF-IC可诱导M2巨噬细胞向M1细胞极化，参与RA病理过程；3）关节腔内注射LF-IC驯化的来源于hFcgRIIa-Tg小鼠巨噬细胞通过诱导Th17细胞分化诱导关节炎；4）LF-IC可通过诱导单核细胞释放颗粒酶B增强单核巨噬细胞的杀肿瘤效应。四年来共有4名硕士和3名博士研究生参与了本项目的研究并顺利毕业。关于LF-IC对单核巨噬细胞的功能影响及其与RA相关性的研究，我们得出LF-IC通过影响滑膜巨噬细胞的表观遗传修饰，使其进入高致敏状态，在RA致病过程中扮演重要作用的假说，部分内容已经在Journal of Immunology、Journal for ImmunoTherapy of Cancer 和Frontier Immunology等SCI收录期刊上发表标注本项目资助的学术论著7篇，另有2篇论文已经修回。这一工作有助于我们对RA致病机理的更深理解，也为RA的治疗提供了新线索和思路。