MMR/CD206: Proteins and Enzymes

MMR (macrophage mannose receptor), also known as MR, CD206, Mrc1, and CLEC13D, is an endocytic receptor that is expressed on M2 alternatively activated macrophages, tumor-associated macrophages (TAMs), inflammatory dendritic cells, and microvascular endothelial cells. MMR internalizes ligands in clathrin-coated vesicles and recycles to the cell surface. It binds LH (luteinizing hormone/lutropin), TSH (thyroid stimulating hormone/thyrotropin), collagens, lysosomal hydrolases, myeloperoxidase, chondroitin sulfates, sulfated N-acetylgalactosamines, and pathogenic microbial branched sugars with terminal mannose, fucose or N-acetylglucosamine. MMR is involved in T cell polarization and production of pro- and anti-inflammatory cytokines. It facilitates peptide presentation on MHC II and cross-presentation on MHC I which is important for tumor immunogenicity.