Macrophages are an important component of the immune system, playing a crucial role in identifying phagocytic pathogens, resisting infections, organogenesis, tissue remodeling, and metabolic adaptation. Recently, the team of Li Hanjie, a researcher of the Chinese Academy of Sciences Shenzhen Institute of Advanced Technology, cooperated with the team of Wang Guanlin, a researcher of the Institute of Metabolic and Integrative Biology of Fudan University, systematically reviewed the latest research progress in the diversity, development and function of human macrophages in recent years, and proposed to study the combination strategy of human tissue resident macrophages by integrating single-cell transcriptomics, spatial transcriptomics, organ like co culture systems, and AI based computing tools. The relevant research results are published in Immunological Trends. The article points out that this strategy will provide new ideas for the treatment of macrophage related diseases, including cancer. The function of the body's "cleaning team" macrophages is adapted to the tissue they reside in and is influenced by the microenvironment they are in. Macrophages are not only the "cleaning team" in the body, clearing pathogens and harmful substances by engulfing cell debris and waste, but also the "sentinel" of the immune system. They release signals such as cytokines to inform other immune cells of foreign invading substances and prepare for battle. Meanwhile, macrophages can also perceive changes in the surrounding environment and maintain body homeostasis based on organ needs. Li Hanjie introduced that rodent models such as mice are powerful tools for studying the origin, differentiation, diversity, and function of resident macrophages in tissues. However, there are significant differences between mice and humans in terms of anatomical structure, complexity of tissue function, and activation of innate and adaptive immune system development. In the past 20 years, researchers have made significant progress in the study of mouse macrophages, but further exploration of the origin, development, and other processes of human macrophages is needed to develop new methods for targeting macrophages to treat human diseases. For a long time, the classification and naming of macrophages within tissues have mainly been based on their location. For example, macrophages appear in the lungs, which are alveolar macrophages. They can engulf various dust particles and microorganisms that enter the alveoli, and rely on the ciliary movement of the respiratory tract to excrete them together with mucus, which is the first line of defense for the body to resist the invasion of foreign microorganisms into the lungs. If macrophages appear in nerve tissue, they are called microglia. They are the most important immune defense line of the central nervous system (CNS), mainly responsible for clearing damaged nerves, plaques, and infectious substances. The research team previously found that in the early stages of development, the transcriptome similarity of macrophages from certain organs is higher, while there are significant differences in the transcriptome of macrophages from other tissues and organs. "A group of macrophages located outside the CNS, now named microglia like cells, have a similar transcriptome to traditional microglia in CNS. This challenges the traditional notion that microglia only differentiate in CNS," said Wang Guanlin. The important direction of cancer treatment research is currently focused on the polarization and functional regulation of macrophages, as well as the interaction between macrophages and the microenvironment. In the tumor microenvironment, macrophages exhibit two distinct states, M1 and M2. M1 macrophages can induce inflammatory responses in tumor tissue and are considered "good" macrophages; On the contrary, M2 macrophages can inhibit tumor immunity. In recent years, CAR-T cell therapy has brought tremendous progress to tumor treatment. However, the application of this method in solid tumors is limited by the lack of tumor specific antigens There are many limitations such as low efficiency in T cell transport and infiltration. Unlike T cells, macrophages can engulf and kill tumor cells without being limited by major histocompatibility complexes. In addition, macrophages exhibit phenotypic and functional plasticity, enabling them to survive in immunosuppressive microenvironments. As antigen-presenting cells, macrophages can also activate T cells by presenting antigens, activate adaptive immune responses, and enhance anti-tumor effects. In terms of safety, macrophages have a lower risk of developing graft-versus-host disease. Therefore, the use of chimeric antigen receptor (CAR) modified macrophages for the treatment of solid tumors is highly anticipated by domestic and foreign researchers. Professors Cheng Tao and Wang Jianxiang from the Hematology Hospital of the Chinese Academy of Medical Sciences (Institute of Hematology, Chinese Academy of Medical Sciences), as well as Professor Li Xin from Sun Yat sen University, have developed an efficient single-layer cell culture system that can generate approximately 6000 megaphages from a single human pluripotent stem cell within 3 weeks. Based on this, CAR macrophages derived from human pluripotent stem cells have been constructed, exhibiting stable CAR expression and effective in vitro anti-tumor activity. The team led by Zhang Jin, a researcher at Zhejiang University, designed an engineered CAR macrophage derived from second-generation induced pluripotent stem cells with enhanced function. They elucidated its antigen-dependent polarization and activation, as well as its mechanism of killing tumors through cell burial, providing a theoretical basis for the application of macrophages in the treatment of solid tumors. At the same time, the treatment of solid tumors with macrophages still faces many challenges, such as the susceptibility of macrophages to polarize into a pro cancer M2 state in the tumor microenvironment, the extremely low gene editing efficiency and long preparation cycle of mature macrophages in patients, and the difficulty in meeting clinical needs in terms of the number of macrophages used for treatment. In addition, how to endow macrophages with non-specific immune function with targeted anti-tumor ability and enhance their therapeutic effect is also a problem that must be solved in the research of macrophages against solid tumors. Exploring more functions to achieve clinical applications. Currently, research on human macrophages faces many challenges, such as sample accessibility, possibility of functional testing, complexity of genetic modifications, and genetic heterogeneity. "The advancement of technologies and analytical methods such as single-cell transcriptomics, spatial transcriptomics, organoid co culture systems, and artificial intelligence based computing tools has provided unprecedented opportunities for studying human macrophages." Li Hanjie said that this has also led to the gradual discovery of the diversity, developmental origins, and functions of macrophages in human tissues. Deep analysis of macrophages in clinical samples helps to understand the role of human macrophages in diseases. The heterogeneity, abundance, phenotype, functional status, and gene expression patterns of macrophages have been shown to be associated with the progression of certain diseases. Wang Guanlin introduced that accurately understanding the characteristic expression patterns of macrophage subtypes in disease status is beneficial for disease diagnosis, prognosis, etc. Furthermore, combined with functional experiments, it can help discover potential therapeutic targets. The use of organoid macrophage co culture systems can effectively help researchers understand how macrophages affect organ development, in vivo balance, and disease progression. Studies on co culturing human brain like organs and inducing macrophages have shown that microglia can regulate neuronal differentiation by providing specific metabolites. With the deepening of research on macrophages, their clinical application prospects in disease diagnosis and treatment will also be broader. For example, early diagnosis of certain diseases can be achieved by detecting biomarkers related to macrophages; By regulating the function of macrophages, precise treatment of diseases can be achieved. (Lai Xin She)