Definition

A humanized peptide ligand of the CD200 activation receptors (CD200ARs), with potential immunostimulating and antineoplastic activities. Upon administration, CD200 activation receptor ligand (CD200AR-L) human P1A8 (hP1A8) targets and binds to CD200ARs complexes on antigen-presenting cells (APCs). This promotes immature dendritic cell (DC) differentiation and cytokine production, and induces a T-cell-mediated immune response against tumor cells. In addition, hP1A8 downregulates the expression of the inhibitory CD200 and PD-1 receptors on APCs and T cells. This inhibits CD200- and PD-1-mediated immunosuppression. CD200, a type 1a transmembrane protein related to the B7 family of co-stimulatory receptors, functions as an immune checkpoint that modulates immune responses through an inhibitory receptor CD200 receptor 1 (CD200R1) and several activation receptors (CD200ARs). It plays an important role in tumor evasion from host immunity.