Figure 1. Mode of action of therapeutic cancer vaccines.

Routes of vaccine administration and migration of immune cells. Antigen-loaded DCs (APCs) travel through the afferent lymph to the lymph nodes, where they prime T cells. The primed, activated T cells migrate through the efferent lymph, thoracic duct, and blood to reach tumor cells. Vaccine-induced T cells must engage with and overcome hostile elements in the cancer microenvironment, including immunosuppressive cells (Tregs, MDSCs) and factors released by the tumor cells, such as immunosuppressive chemokines and cytokines and IDO, which impair T cell migration, function, and expansion.