Recombinant Mouse CD200R1 Fc Chimera Protein, CF

CD200 R1, also known as OX-2 receptor, is a 90 kDa, type I transmembrane protein that belongs to the immunoglobulin superfamily. CD200 R1 is important in the regulation of myeloid cell activity (1-3). The mouse CD200 R1 cDNA encodes a 326 aa precursor that includes a 25 aa signal sequence, a 213 aa extracellular domain (ECD), a 21 aa transmembrane segment, and a 67 aa cytoplasmic domain. The ECD is composed of one Ig-like V-type domain and one Ig-like C2-type domain (4). Within the ECD, mouse CD200 R1 shares 56% and 70% aa sequence identity with human and rat CD200 R1, respectively. The ECD of mouse CD200 R1 shares 69%, 38%, 79%, and 83% aa sequence identity with the ECD of CD200 R2, 3, 4, and a CD200 R-like molecule, respectively. CD200 R1 is expressed primarily on mast cells, basophils, macrophages, and dendritic cells, (5-7) while its ligand, CD200, is widely distributed (8). Disruption of this receptor-ligand pair by knockout of the CD200 gene leads to increased macrophage number and activation, plus a predisposition to autoimmune disorders (9). Association of CD200 with CD200 R1 takes place between their respective N-terminal Ig-like domains (10). The CD200 R-like molecules may interact differently with CD200 (11, 12). The cytoplasmic domain of CD200 R1 contains two non-ITIM tyrosine residues which are required for propagating its inhibitory signals (13-15). CD200 R-like molecules, in contrast, are potentially activating receptors by means of their association with DAP12 (4, 16).