PD-1, also known as programmed cell death protein 1 or CD279 (cluster of differentiation 279), is a cell surface receptor, a member of the immunoglobulin superfamily, expressed on T cells and B cells. As the most important ligand of PD-1, PD-L1 is expressed in almost all tumor cell lines. As an immune checkpoint, PD-1 is involved in the progression of a variety of tumors. The combination of PD1 and PD-L1 can inhibit the proliferation and activation of CD4-positive T cells and CD8-positive T cells, and mediate the down-regulation of interleukin (IL)-2 and interferon (IFN)-γ secretion, and ultimately inhibit T cell immune function , To form an immunosuppressive tumor microenvironment, allowing tumor cells to obtain immune escape.
Blocking the PD1/PD-L1 signaling pathway can reverse the immunosuppressive tumor microenvironment, restore the anti-tumor activity of T cells, and enhance the anti-tumor effect of the body's immune system  . At present, a number of clinical studies [2-4] have verified that blocking the PD1/PD-L1 pathway has a good anti-tumor effect.
Icartab is committed to the research and development of tumor antibody drugs. Our company has independently constructed a PD-1 / PD-L1 blocking activity detection reporter gene system. The reporter gene method can be used to determine different types of anti-PD-1 /PD-L1 Biological activity of mAb. This experiment contains two genetically engineered cell lines:
• PD-1 effector cells: Jurkat cells expressing human PD-1 and NFAT-RE
• aAPC CHO-PDL1 cells: CHO cells expressing human PD-L1 and CD3 antibodies.
When Jurkat effector cells are co-cultured with aAPC CHO-PDL1, the PD-1/PD-L1 interaction will inhibit TCR signaling and NFAT-RE-mediated luminescence. Adding PD-1 or PD-L1 antibodies with blocking activity will release inhibitory signals, resulting in TCR activation and NFAT-RE-mediated luminescence (as shown in the figure below). Bio-Glo™ reagents can be used for detection and quantification.
Illustration: When the two cells are incubated together, the anti-CD3ScFv on the surface of the CHO cell binds to the CD3 molecule on the membrane of the Jurkat cell, which transmits the activation signal inward, while the PD-L1 on the surface of the CHO cell binds to the PD-1 molecule on the surface of the Jurkat cell. Inhibit the transmission of activation signals, and the luciferase reporter gene cannot be expressed. These two cells were used to simulate the mechanism by which T cell activation is inhibited by the PD-1 signaling pathway. When anti-PD-1/PD-L1 antibody is added, the combination of PD-1 and PD-L1 is blocked, and the surface of CHO cells is resistant to CD3ScFv and the membrane CD3 molecules of Jurkat cells combine to transmit activation signals, and NFAT-driven luciferase reporter gene is expressed.
1.Ma W, Gilligan BM, Yuan J, et al. Current status and perspectives in translational biomarker research for PD-1/PD-L1 immune checkpoint blockade therapy. J Hematol Oncol. 2016;9(1):47. DOI: 10.1186/s13045-016-0277-y
2.Fehrenbacher L, Spira A, Ballinger M, et al. Atezolizumab versus docetaxel for patients with previously treated non-small-cell lung cancer (POPLAR): a multicentre, open-label, phase 2 randomised controlled trial. Lancet. 2016;387(10030):1837-1846. DOI: 10.1016/S0140-6736(16)00587-0
3.Motzer RJ, Escudier B, McDermott DF, et al. Nivolumab versus Everolimus in Advanced Renal-Cell Carcinoma. N Engl J Med. 2015;373(19):1803-1813. DOI: 10.1056/NEJMoa1510665
4.Herbst RS, Baas P, Kim DW, et al. Pembrolizumab versus docetaxel for previously treated, PD-L1-positive, advanced non-small-cell lung cancer (KEYNOTE-010): a randomised controlled trial. Lancet. 2016;387(10027):1540-1550. DOI: 10.1016/S0140-6736(15)01281-7