树突状细胞的脂膜对固态颗粒的感知

Protein based receptor ligand interactions are universally regarded as the initiating point of immune activation. However, it is questionable if it is applicable to immune recognition of solid structures. This issue is particularly relevant in vaccine design as some of the best known adjuvants are solid crystals, such as alum and monosodium urate. Binding of particulate antigens by antigen presenting cells (APC) is a critical step in immune activation. It has been demonstrated that uric acid and alum crystals are potent adjuvants, initiating a robust adaptive immune response. However, the mechanisms of activation are unknown. Using atomic force microscopy as a tool for real time single cell activation analysis, we have collected evidence that uric acid and alum crystals can directly engage cellular membranes, with a force substantially stronger than protein based cellular contacts. Binding of particulate substances activates Syk kinase-dependent signaling in dendritic cells (DCs). These observations suggest a mechanism whereby immune cell activation can be triggered by solid structures via membrane lipid alteration without the requirement for specific cell surface receptors, and a testable hypothesis for crystal-associated inflammation and adjuvanticity. In this proposal, we extend the findings to study the signaling mechanisms involved, particularly the association between cell surface lipid sorting and downstream signal transduction, critical steps in crystal mediated immune activation, as well as how this mechanism affects antigen presentation. The outcome of this work will impact vaccine development and our understanding of crystal related diseases.

受体配体之间的相互作用一般被认为是免疫激活的起点，然而，这一方式是否适用于免疫细胞对固体结构的感知是值得怀疑的。因为一般常见的免疫佐剂是晶体，如明矾和尿酸钠，这个课题对免疫激活，特别是疫苗的发展有相关的意义。固体结构和APC的结合是改变免疫激活的一个关键步骤。虽然上述晶体已被证明是强有力的佐剂，其原因尚未清楚。利用原子力显微镜进行实时单细胞活化分析，我们已报道了这些晶体可以和APCde胞膜直接结合，而且结合力比蛋白质之间的相互作用要强，颗粒物质和脂膜结合后激活SYK激酶及下游信号机制。这些发现提示一个机制，并且通过膜和固体之间相互作用的免疫感知方法。我们希望能够开拓这方面的探索，理清信号通路，特别是膜上的脂质重排和下游信号的关系，以及他们在抗原呈递中起到的作用，此项研究成果对疫苗开发和晶体源发的炎症是有重大意义的。

受体配体之间的相互作用一般被认为是免疫激活的起点，然而，这一方式是否适用于免疫细胞对固体结构的感知是值得怀疑的。固体结构和APC的结合是改变免疫激活的一个关键步骤。虽然许多晶体晶体已被证明是强有力的佐剂，其激活机理尚未清楚。利用原子力显微镜进行实时单细胞活化分析，我们已报道了这些晶体可以和抗原呈递细胞细胞膜直接结合，激活SYK激酶及下游信号机制。这些发现提示一个通过膜和固体之间相互作用的免疫感知方法。通过这个项目，我们在相关方面取得了新的进展。我们首先发现固体颗粒和细胞膜结合可以改变PIP2的重组，这个现象驱动细胞内Moesin向细胞膜的转移。而Moesin中的ITAM序列可以吸引Syk，起到免疫激活的作用。我们同时发现固体颗粒的激活可以直接造成炎症小体的激活和诱发可溶性抗原的交叉呈递。另外，树突状细胞细胞膜上的力学效应可以改变它们刺激T细胞的能力，比如调节性T细胞和树突状细胞的强烈结合使后者不能有效接触其他T细胞，从而揭示了调节性T细胞的作用机制。