CD4 and neoplasm: Many studies have shown that tumor cells and dendritic cells (DCs)-derived exosomes carry a large number of tumor-associated markers, such as major histocompatibility complex class I molecules (MHC I) and heat shock proteins (HSP, HSP70, HSP50), which serve as essential signals for T cell activation (Fan et al., 2022), and producing antitumor immune responses in CD4+ T cells and CD8+ T cells.