The RMP1-14-CP162monoclonal antibody is a chimeric version of the original RMP1-14antibody。The variable domain sequences are identical to the original RMP1-14but the constant region sequences have been switched from rat IgG2a to mouse IgG1。The RMP1-14-CP162antibody contains no Fc mutations just as the original rat IgG2a antibody does not。RMP1-14-CP162reats with mouse PD-1（programmed death-1）also known as CD279。PD-1is a50-55kDa cell surface receptor encoded by the Pdcdcd1gene that belongs to the CD28family of the Ig superfamily。PD-1is transiently expressed on CD4and CD8thymocytes as well as activated T and B lymphocytes and myeloid cells。PD-1expression declines after successful elimination of antigen。Additionally，Pdcd1mRNA is expressed in developing B lymphocytes during the pro-B-cell stage。PD-1’s structure includes a ITIM（immunoreceptor tyrosine-based inhibitory motif）suggesting that PD-1negatively regulates TCR signals。PD-1signals via binding its two ligands，PD-L1and PD-L2both members of the B7family。Upon ligand binding，PD-1signaling inhibits T-cell activation，leading to reduced proliferation，cytokine production，and T-cell death。Additionally，PD-1is known to play key roles in peripheral tolerance and prevention of autoimmune disease in mice as PD-1knockout animals show dilated cardiomyopathy，splenomegaly，and loss of peripheral tolerance。Induced PD-L1expression is common in many tumors including squamous cell carcinoma，colon adenocarcinoma，and breast adenocarcinoma。PD-L1overexpression results in increased resistance of tumor cells to CD8T cell mediated lysis。In mouse models of melanoma，tumor growth can be transiently arrested via treatment with antibodies which block the interaction between PD-L1and its receptor PD-1。For these reasons anti-PD-1mediated immunotherapies are currently being explored as cancer treatments。
