By Laura McAleer and Catriona Thomson
Programmed cell death protein 1 (PD-1) is an immune checkpoint that can be found on cells involved in regulating the immune system’s response to self cells by down regulating the immune response and promoting self tolerance by suppressing T cell inflammatory activity. Therefore, PD-1 has an important role in preventing autoimmune diseases but can also prevent the immune system from killing cancer cells. PD-1, which can be found on T cells and some B cells, normally interacts with its two ligands PD-L1 and PD-L2, found on antigen-presenting cells and tumor cells. Many new therapies are targeting the PD-1 pathway to boost the immune response to cancer cells.
Current assays used to measure the activity of anti-PD-1 or anti-PD-L1 antibodies rely on primary human T cells and measurement of functional endpoints such as cell proliferation, interferon gamma (IFNγ) and interleukin-2 (IL-2) production. These assays can be highly variable due to their reliance on primary cells and complex assay protocols. One method to demonstrate the activity of anti PD-1 molecules using a functionally relevant but less variable method is using a potency ELISA.