Immunotherapy has revolutionized cancer treatment and rejuvenated the field of tumor immunology. Several types of immunotherapy, including adoptive cell transfer (ACT) and immune checkpoint inhibitors (ICIs), have obtained durable clinical responses, but their efficacies vary, and only subsets of cancer patients can benefit from them. Immune infiltrates in the tumor microenvironment (TME) have been shown to play a key role in tumor development and will affect the clinical outcomes of cancer patients. Comprehensive profiling of tumor-infiltrating immune cells would shed light on the mechanisms of cancer–immune evasion, thus providing opportunities for the development of novel therapeutic strategies. However, the highly heterogeneous and dynamic nature of the TME impedes the precise dissection of intratumoral immune cells. With recent advances in single-cell technologies such as single-cell RNA sequencing (scRNA-seq) and mass cytometry, systematic interrogation of the TME is feasible and will provide insights into the functional diversities of tumor-infiltrating immune cells. In this review, we outline the recent progress in cancer immunotherapy, particularly by focusing on landmark studies and the recent single-cell characterization of tumor-associated immune cells, and we summarize the phenotypic diversities of intratumoral immune cells and their connections with cancer immunotherapy. We believe such a review could strengthen our understanding of the progress in cancer immunotherapy, facilitate the elucidation of immune cell modulation in tumor progression, and thus guide the development of novel immunotherapies for cancer treatment.

免疫疗法彻底改变了癌症治疗并重振了肿瘤免疫学领域。包括过继细胞移植（ACT）和免疫检查点抑制剂（ICIs）在内的几种类型的免疫疗法已获得持久的临床反应，但其疗效各不相同，并且只有部分癌症患者可以从中受益。肿瘤微环境（TME）中的免疫浸润已被证明在肿瘤发展中发挥关键作用，并将影响癌症患者的临床结果。对肿瘤浸润免疫细胞的全面分析将揭示癌症免疫逃避的机制，从而为开发新的治疗策略提供机会。然而，TME 的高度异质性和动态性阻碍了瘤内免疫细胞的精确解剖。随着单细胞 RNA 测序 (scRNA-seq) 和质谱流式细胞术等单细胞技术的最新进展，对 TME 进行系统性检测是可行的，并将为了解肿瘤浸润免疫细胞的功能多样性提供见解。在这篇综述中，我们概述了癌症免疫治疗的最新进展，特别是重点关注具有里程碑意义的研究和肿瘤相关免疫细胞的最新单细胞表征，并总结了肿瘤内免疫细胞的表型多样性及其与癌症免疫治疗的联系。我们相信这样的综述可以加强我们对癌症免疫治疗进展的理解，有助于阐明肿瘤进展中的免疫细胞调节，从而指导癌症治疗的新型免疫疗法的开发。