细胞间的细胞外通讯，亦称为细胞间相互作用，对生物体的存活起着重要作用。这种通讯通过不同的方式进行，其中一种方式是利用细胞外囊泡。最近发现，小的脂质细胞外囊泡——外泌体，在体内细胞之间的信号传导中发挥作用。这些囊泡中包含重要的生物活性分子，包括脂质、蛋白质、DNA、mRNA和非编码RNA，如微小RNA（miRNA）。所有细胞，包括免疫细胞（巨噬细胞、淋巴细胞、粒细胞、树突细胞、肥大细胞）和肿瘤细胞，都会分泌外泌体。肿瘤微环境（TME）是支持肿瘤细胞生长的复杂网络。该微环境包括肿瘤细胞本身、细胞外基质、成纤维细胞、内皮细胞、血管、免疫细胞以及外泌体和细胞因子等非细胞组分。本综述旨在深入探讨免疫系统如何在内部及与其他细胞类型之间进行通讯的最新发现，特别关注巨噬细胞、树突细胞、B淋巴细胞和T淋巴细胞中外泌体miRNA的研究。此外，我们将探讨外泌体miRNA在肿瘤微环境中的作用及其免疫调节效应。© 2023. 中华民国（台湾）国家科学委员会。

Extracellular communication, in other words, crosstalk between cells, has a pivotal role in the survival of an organism. This communication occurs by different methods, one of which is extracellular vesicles. Exosomes, which are small lipid extracellular vesicles, have recently been discovered to have a role in signal transduction between cells inside the body. These vesicles contain important bioactive molecules including lipids, proteins, DNA, mRNA, and noncoding RNAs such as microRNAs (miRNAs). Exosomes are secreted by all cells including immune cells (macrophages, lymphocytes, granulocytes, dendritic cells, mast cells) and tumor cells. The tumor microenvironment (TME) represents a complex network that supports the growth of tumor cells. This microenvironment encompasses tumor cells themselves, the extracellular matrix, fibroblasts, endothelial cells, blood vessels, immune cells, and non-cellular components such as exosomes and cytokines. This review aims to provide insights into the latest discoveries concerning how the immune system communicates internally and with other cell types, with a specific focus on research involving exosomal miRNAs in macrophages, dendritic cells, B lymphocytes, and T lymphocytes. Additionally, we will explore the role of exosomal miRNA in the TME and the immunomodulatory effect.© 2023. National Science Council of the Republic of China (Taiwan).