Immuno-oncology has moved from an emerging field to one of the cornerstones of cancer therapy. Unlike traditional therapies such as radiation or chemotherapy which target the tumor itself, immunotherapy stimulates the patient’s own immune system to target and eradicate cancerous cells. In order to attack cancerous cells, the immune system must be able to respond in several ways. First, antigen presenting cells (APC) such as macrophages and dendritic cells must process tumor associated antigens (TAA) derived from dying cancer cells and display them on their surface via MHC-II receptors. Second, antigen presenting cells must generate a protective T-cell population. Last, cancer-specific, CD8+ cytotoxic T-cells must evade immunosuppressive (checkpoints) signals being expressed in the tumor.

Early immunotherapy ideas involved using vaccines to present tumor associated antigens to APCs. Recently, the most exciting therapies have involved clearing the immunosuppressive signals within the tumor using checkpoint inhibitors. Successful inhibition of the PD-1 and CTLA-4 signaling systems have revolutionized treatment options. The identification of other receptor systems such as Tim-3, Lag-3, and OX40, which down regulate T-cells, has expanded the possibility of new checkpoint inhibitors.