CD200 is a type-1 membrane glycoprotein, which contains two immunoglobulin domains, and thus belongs to the immunoglobulin superfamily. Studies of the related genes in mouse and rat suggest that this gene may regulate myeloid cell activity and delivers an inhibitory signal for the macrophage lineage in diverse tissues. Multiple alternatively spliced transcript variants that encode different isoforms have been found for this gene. Recombinant human CD200 protein, fused to His-tag at N-terminus, was expressed in E.coli.