Functions of human memory B cells and the diversity of the memory B cell population

记忆B细胞（MBC）在体液免疫中起核心作用。人类MBC的不同亚群已被确定，包括类别转换，IgM+IgD+ CD 27+，和IgM-只有MBC，但他们的具体特点和功能知之甚少。我们生成了幼稚B细胞和MBC的三个主要亚群的基因表达谱，并揭示了数百个差异表达的基因和功能相关基因集的不同表达。我们的目标是验证这些数据，并对特定基因进行功能研究，以检验不同MBC子集具有不同特征并实现特定和独特功能的假设。进一步的准备工作表明，类别转换和IgM+IgD+ CD 27 + MBC可以来自共同的生殖中心B细胞克隆。然而，仍然没有关于MBC群体的复杂性和克隆内多样性的全面知识，以及不同的MBC子集是否源自相同或不同的免疫应答。因此，本申请的第二个主要目的是通过对来自人MBC的五个子集的免疫球蛋白V区基因进行下一代测序来阐明这些问题。在第三部分中，我们将通过细胞分选分离抗原特异性记忆B细胞，并确定其克隆复杂性和抗原特异性克隆相关IgG+和IgM+ MBC的存在。总之，这些研究将为人类MBC的产生和功能提供重要的新见解，并为更好地理解疾病中失调的体液免疫系统奠定基础。

Memory B cells (MBC) play a central role in humoral immunity. Distinct subpopulations of human MBC have been identified, including class-switched, IgM+IgD+CD27+, and IgM-only MBC, but their specific features and functions are poorly understood. We generated gene expression profiles of naïve B cells and the three main subsets of MBC and revealed hundreds of differentially expressed genes and different expression of functionally linked genesets. We aim to validate these data and perform functional studies for particular genes to test the hypothesis that the distinct MBC subsets have different features and fulfil specific and distinct functions. Further preparatory work revealed that class-switched and IgM+IgD+CD27+ MBC can derive from common germinal centre B cell clones. However, there is still no comprehensive knowledge about the complexity and intraclonal diversity of the MBC population, and whether distinct MBC subsets derive from the same or distinct immune responses. Therefore, the second main aim of this application is to clarify these issues by next generation sequencing of immunoglobulin V region genes from five subsets of human MBC. In a third part, we will isolate antigen-specific memory B cells by cell sorting and determine their clonal complexity and the existence of antigen-specific clonally related IgG+ and IgM+ MBC. Together, these studies will give essential novel insights into MBC generation and function in the human, and also set a basis for a better understanding of a disregulated humoral immune system in diseases.