CD279, or programmed cell death protein 1 (PD-1), is a 55 kD member of the immunoglobulin superfamily with an immunoreceptor tyrosine-based inhibitory motif (ITIM) in its cytoplasmic region. It is mainly expressed on activated T cells, B cells and myeloid cells, and negatively regulates immune responses by binding to its ligands PD-L1 (B7-H1) and PD-L2 (B7-DC), thereby inhibiting T cell proliferation and cytokine secretion. Dysregulatio of the PD-1 pathway is linked to autoimmune diseases (e.g, rheumatoid arthritis, systemic lupus erythematosus) and tumor immune escape, makin it a key target for cancer immunotherapy. The antibody PE, anti-Human CD279 (PD-1)-AS630 binds specifically to CD279, facilitating relevant research.