OX-2 membrane glycoprotein

CD200 (OX-2 membrane glycoprotein) is a cell surface glycoprotein that costimulates T-cell proliferation and may regulate myeloid cell activity across various tissues (UniProt: P41217). The protein functions as an immunomodulatory molecule with roles in immune cell interactions and tissue-resident immune homeostasis.

CD200 is broadly expressed across tissues and participates in immune regulation pathways. It has established roles in controlling myeloid cell responses, particularly in the central nervous system where it interacts with CD200 receptor on microglia and macrophages to maintain immune quiescence (UniProt: P41217).

CD200 shows reduced abundance in Alzheimer's Disease brain tissue. In a human post-mortem study comparing AD brains to age-matched controls using TMT-labeled quantitative proteomics across subcellular fractions, CD200 was significantly down-regulated with a mean log2 fold-change of −0.75 (Chaparral AD proteomics). This down-regulation may reflect altered immune regulation and microglial activation state in the AD brain, supporting investigation of CD200-mediated immunomodulation in neurodegeneration.