Apoptosis or Programmed cell death is known as a conserved gene-directed mechanism for the specific elimination of unnecessary or unwanted cells from an organism and is involved in many immune system mechanisms and diseases. The main differences of this pathway with cell necrosis as two main pathways for elimination of unwanted cells are the absence of inflammation and the restricted effect on target cells. Apoptosis has an important role in biological processes such as normal development, tissue homeostasis, elimination of destroyed cells or virus infected cells and remove of self antigen-activated immune cells. Apoptosis is important for regulation of cell growth and proliferation, development and body health and many autoimmune diseases, cancers and viral infections are the result of impaired or inhibited Programmed cell death. Therefore the main objective of apoptosis research is to identify molecular components and regulatory mechanisms specially Bcl-2 and IAP family as the most important regulators of apoptosis and this information may lead to application of therapeutic agents that can modulate this process in the treatment of neurodegenerative disorders and proliferative diseases such as cancer.

Background: The Programmed cell death protein 1 (PD-1), which is a member of the CD28 receptor family, can negatively regulate antitumor immune responses by interacting with its ligands, PD-L1 or PD-L2. The PD-1– PD-L1 signaling pathway is a checkpoint mechanism that plays essential roles in downregulating immune responses in cancerous tissues. Thus, blocking this signaling pathway leads to enhanced antitumor immunity, potentially preventing tumor progression. Methods: We synthesized the extracellular domain of the PD-1 receptor (rPD-1) de novo by using a two-step polymerase chain reaction and the Phusion® DNA polymerase. The synthesized gene was cloned into the pET28 expression plasmid and transformed into competent Escherichia coli. Purification of rPD-1 was performed by metal-affinity chromatography, using a HisTrap column. Purified rPD-1 was characterized by western blotting and mass spectrometry using the SwissProt database and the Mascot program. Results: Designed and synthesized construct of rPD-1 was 500 bp in size. Analysis of the electrophoresis data of purified rPD-1 showed the presence of a protein with a molecular mass of 21 kDa. Mass spectrometry data using the SwissProt database and the Mascot program outputted the highest-scoring sequence to correspond to rPD-1. Conclusions: Synthesized de novo rPD-1 may have potential therapeutic applications in enhancing antitumor immune responses.