CD4 and neoplasm: In addition, tumor cell-derived vesicles inhibit the function of immune cells through various mechanisms, such as carrying FasL and TRAIL molecules, directly inducing apoptosis of dendritic cells (DCs), effector CD4+ and CD8+ T lymphocytes, or inducing regulatory T cell expansion by carrying upregulated circular RNA GSE1, thereby suppressing anti-tumor immune responses (Markov et al., 2019).