在其传播过程中，循环肿瘤细胞(CTCs)稳定地面对免疫系统，免疫系统是整个转移级联过程中的关键因素，包括从入血至CTCs对远处部位的定植。在本章中，我们将描述参与这一有争议的对话的免疫细胞，这一对话涵盖了天然杀伤细胞(NK细胞)、CD4+和CD8+ T淋巴细胞、T辅助17细胞、调节性T细胞、中性粒细胞、单核细胞、巨噬细胞、髓源性抑制性细胞、树突状细胞和血小板等多种循环免疫效应细胞介导的抗肿瘤活性以及促肿瘤和免疫抑制功能。然后，我们将从CTCs的角度报告相同的相互作用，描述与上述免疫细胞之间的直接和间接相互作用机制。最后，我们将报道最近的文献证据，论述集成CTCs和免疫细胞监测在癌症患者管理中的潜在预后作用。版权所有 © 2023。Elsevier Inc.出版。

During their dissemination, circulating tumor cells (CTCs) steadily face the immune system, which is a key player in the whole metastatic cascade, from intravasation to the CTC colonization of distant sites. In this chapter, we will go through the description of immune cells involved in this controversial dialogue encompassing both the anti-tumor activity and the tumor-promoting and immunosuppressive function mediated by several circulating immune effectors as natural killer (NK) cells, CD4+ and CD8+ T lymphocytes, T helper 17, regulatory T cells, neutrophils, monocytes, macrophages, myeloid-derived suppressor cells, dendritic cells, and platelets. Then, we will report on the same interaction from the CTCs point of view, depicting the direct and indirect mechanisms of crosstalk with the above mentioned immune cells. Finally, we will report the recent literature evidence on the potential prognostic role of the integrated CTCs and immune cells monitoring in cancer patients management.Copyright © 2023. Published by Elsevier Inc.