Mannose receptor C type 1 and Complement receptor 3 (MRC1 / CR3)

The Mannose receptor / putative CR3-related receptor refers to a dual-receptor system on the surface of macrophages, primarily composed of the Mannose Receptor C type 1 (MRC1, also known as CD206) and Complement Receptor 3 (CR3, an integrin composed of CD11b and CD18). This terminology originates from early research into the attachment mechanisms of pathogens such as Pneumocystis carinii and Leishmania species, which exploit these receptors to gain entry into host cells. The Mannose Receptor is a C-type lectin that recognizes terminal mannose, fucose, and N-acetylglucosamine residues, while CR3 is an integrin that binds the complement fragment iC3b as well as various microbial surface molecules. Together, they facilitate the phagocytosis of pathogens, though some organisms use this pathway to avoid intracellular destruction by modulating phagosome maturation. While not typically targeted by small-molecule drugs, these receptors are significant in the context of infectious diseases and are explored as targets for mannosylated drug delivery systems and immunomodulatory therapies. For instance, the Mannose Receptor is utilized for diagnostic imaging via agents like Technetium Tc 99m tilmanocept, which binds specifically to CD206.

Other names

CD206CD11b/CD18Mac-1Macrophage mannose receptorMRC1ITGAM/ITGB2Putative CR3-related receptor

Binding to extracellular domains (CTLDs for MRC1 or the I-domain for CR3) to facilitate internalization for diagnostic imaging or to modulate cell adhesion and phagocytosis.