Checkpoint Inhibitors

The human immune system fights not only external pathogens but also clears internal abnormalities like dying and cancer cells. The cancer immunity cycle begins when antigens produced by tumor cells are processed by dendritic cells for antigen presentation. This is followed by additional signals that activate and induce an anti-tumor response by T cells, eventually resulting in the killing of tumor cells.

To prevent over-stimulation in the presence of antigens associated with tumor cells, the immune system has several receptors that negatively regulate its functions. Referred to as checkpoint receptors, these control the initiation of a productive immune response and prevent excessive T cell activation that could lead to inflammatory autoimmune processes. However, tumor cells often utilize immune checkpoints to favour growth. The blocking of checkpoint receptors like CTLA-4 or PD-1 allows the immune system to overcome its regulatory mechanisms and provide a robust anti-tumor response. Conversely, the activation of checkpoint receptors in autoimmune diseases helps in reducing inflammation.