CD4 and neoplasm: These miR‐34a‐enriched exosomes stimulated CD8+ T cell activation by reducing the expression of immune evasion markers, such as PD‐L1, in the tumor microenvironment, leading to an increased CD8+/CD4+ T cell ratio and enhancing anti‐tumor immune responses in vivo.[113] In another study, nanovaccine was developed using exosomes derived from immunogenically dying PANC‐02 PCa cells, engineered with MART‐1 peptides on the surface and loaded with CCL22 siRNA through electroporation.