Emergence of immunotherapy as a novel way to treat hepatocellular carcinoma

Figure 4 Tumor-associated antigen presentation of antigen-presenting cells to T cells. Endogenous antigens are degraded to peptides and loaded on MHC class II on APCs to be presented to the CD4⁺ T cells, while exogenous antigens are degraded to peptides and loaded on MHC class I to be presented to the CD8⁺ T cells. These pathways deliver activation signals to corresponding T cells. However, full activation and subsequent survival require the co-stimulatory signals delivered by several pathways including the CD80/CD86-CD28 pathway. In the absence of co-stimulatory signals, T cells become unresponsive to the antigen, a condition called anergy. TAA: Tumor-associated antigen; APCs: Antigen-presenting cells.