Sample Solution

PD-1 is expressed on a variety of immune cells including monocytes, T and B cells, dendritic cells and tumor infiltrating lymphocytes. PD-1 has two ligands: PD-L1 and PD-L2. PD-L1 is typically expressed on antigen presenting cells (APCs) and tumor cells. The binding of PD-L1 to PD-1 initiates antigen receptor signalling transduction leading to the destruction of T-cell metabolism and ultimately eliminates the immune function of T-cells. Some cancer cells have large amounts of PD-L1 which helps them evade immune attack. PD-L2 on the other hand is expressed on dendritic cells and monocytes and binds with a higher affinity to PD-1 than PD-L1.

Loss of immunologic control is a hallmark of cancer and the engagement of PD-L1 with PD-1 prevents the immune system from attacking tumor cells. Monoclonal antibodies (mAbs) that target either PD-1 or PD-L1 block this interaction and boost the body’s natural immune response against cancer cells. These antibodies act as tumor suppressing factors and enhance the antitumor immune response. This immune response starts with tumor cells producing mutated antigens that dendritic cells use to prime T-cells and stimulate the activation of cytotoxic T-cells. Activated T-cells then travel to and infiltrate the tumor environment and bind to the cancer cells. The bound effector T-cells then release cytotoxins, which induce apoptosis in their target cancer cells.

Typically, antibodies directed towards PD-1 are not preferred as they prevent its binding to