Cancer Vaccine Perfect Paragraph

Cancer vaccine immunotherapies exploit the cross-presentation function of the immune system that allows antigen-presenting cells (APCs), especially dendritic cells (DCs), to phagocytose extracellular tumor-associated antigens (TAAs) and display them with MHC class I molecules to CD8+ T cells. Typically, extracellular antigens are phagocytosed by APCs and presented through MHC class II to CD4+ T cells, while endogenous antigens are presented through MHC class I to CD8+ T cells. This ability to display injected extracellular TAAs on MHC I is crucial in the activation of CD8+ T cells and subsequent eradication of the tumor. There are currently two known routes in the immune system for this mechanism of cross-presentation: cytosolic and vacuolar (Immune Response 2014). In the cytosolic route, the extracellular antigen is phagocytosed and then actively transported to the cytosol, where it is cleaved by a proteasome, transported to the ER, loaded onto MHC class I, and displayed on the plasma membrane. In the vacuolar route, the extracellular antigen is phagocytosed and at the ER is incorporated into an early endosome with lysosomal enzymes and MHC class I, which subsequently displays the antigen on the plasma membrane (Immune Response 2014). Further research is necessary to understand specific pathways involved in this cross-presentation mechanism.