As an important part of the human body, the immune system is closely related to the occurrence of diseases. Based on the traditional classification methodology, it is mainly divided into two branches: innate immunity and adaptive immunity. Innate immune cells mainly include monocytes (Mono), natural killer (NK) cells and dendritic cells (DC). The adaptive immune cells mainly include B lymphocytes (B) and T lymphocytes (T). Peripheral blood mononuclear cells (PBMCs) mainly include T cells, B cells, NK cells, Mono cells and DC cells.~The proportion of these cell populations varies among individuals. Usually in PBMC, T lymphocytes account for 45-70%, B cells account for 5-15%, NK cells account for 5-20%, Mono cells account for 10-30%, and DC cells account for 1-2%. Among them, B cells can be divided into transitional, naive, memory subgroups and plasma cells. While, T cells are mainly composed of cluster of differentiation 4+ (CD4+) T cells and cluster of differentiation 8+ (CD8+) T cells with the ratio about 2:1. What's more, CD4+ T cells and CD8+ T cells can be further divided into naive cells, central memory cells in contact with antigen, effector memory cells and effector cells. Mono cells can be divided into classic monocytes and non-classical cluster of differentiation 16+ (CD16+) pro-inflammatory monocytes. DC cells include plasmacytic dendritic cells (pDC) and myeloid dendritic cells (mDC).~In recent years, scRNA-seq has developed rapidly and is widely used in research related to the immune system, breaking traditional cognition and gaining a new understanding of immune cell classification. In particular, the emerging scRNA-seq provides new ideas for the study of cell heterogeneity in multicellular organisms. Analyzing the changes in the expression profile of the cell transcriptome at the single-cell level can clearly show the changes in the trajectory of individual cells, reveal new cell types, and discover the potential functions of immune cells.~Adults have a relatively stable immune system, with little interference from the external environment. Therefore, this study intends to recruit healthy adults and use multi-omics techniques such as scRNA-seq to systematically classify the PBMCs of healthy adults to provide a basis for further disease-related research.
In recent years, single-cell high-throughput sequencing technology has developed rapidly and is widely used in research related to the immune system, breaking traditional cognition and gaining a new understanding of immune cell classification. In particular, the emerging single cell RNA sequencing (scRNA-seq) provides new ideas for the study of cell heterogeneity in multicellular organisms. Analyzing the changes in the expression profile of the cell transcriptome at the single-cell level can clearly show the changes in the trajectory of individual cells, reveal new cell types, and discover the potential functions of immune cells. Therefore, this study intends to recruit healthy adults and use multi-omics techniques such as single-cell sequencing to systematically classify the peripheral blood mononuclear cells of healthy adults to provide a basis for further disease-related research.