CD4⁺ T cells exhibit diverse functions in cancer surveillance. Concordantly, single-cell transcriptional analyses have revealed several distinct CD4⁺ T-cell differentiation states in tumours, including cytotoxic and regulatory subsets associated with favourable or unfavourable outcomes, respectively. These transcriptional states are determined and further shaped by dynamic interactions of CD4⁺ T cells with different types of immune cells, stromal cells and cancer cells. Therefore, we discuss the cellular networks in the tumour microenvironment (TME) that either promote or impede CD4⁺ T-cell cancer surveillance. We consider antigen/Major histocompatibility complexclass-II (MHC-II)-dependent interactions of CD4⁺ T cells with both professional antigen-presenting cells and cancer cells, the latter of which can directly express MHC-II, at least in some tumours. Additionally, we examine recent single-cell RNA sequencing studies that have shed light on the phenotype and functions of cancer-specific CD4⁺ T cells in human tumours.

CD4 ⁺ T 细胞在癌症监测中表现出多种功能。一致地，单细胞转录分析揭示了肿瘤中几种不同的 CD4 ⁺ T 细胞分化状态，包括分别与有利或不利结果相关的细胞毒性和调节子集。^{这些转录状态由 CD4 +} T 细胞与不同类型的免疫细胞、基质细胞和癌细胞的动态相互作用决定并进一步形成。因此，我们讨论肿瘤微环境 (TME) 中促进或阻碍 CD4 ⁺ T 细胞癌症监测的细胞网络。^{我们考虑 CD4 +} T 细胞与专业抗原呈递细胞和癌细胞之间抗原/主要组织相容性复合物 II 类 (MHC-II) 依赖性相互作用，后者至少在某些肿瘤中可以直接表达 MHC-II。此外，我们还研究了最近的单细胞 RNA 测序研究，这些研究揭示了人类肿瘤中癌症特异性 CD4 ^{+ T 细胞的表型和功能。}