RPL17 and infection: PD − 1 (programmed death receptor − 1), an important immunosuppressive molecule, belongs to the immunoglobulin superfamily and is a membrane protein with 288 amino acid residues.Immunoregulation targeting PD − 1 has great significance in inhibiting tumors, infections, and autoimmune diseases and protecting organ transplantation survival.The ligand PD − L1 also acts as a target, as do corresponding antibodies.The expression of PD − L1 on tumor cells inhibits antitumor activity through the binding of PD − 1 to effect T cells.