MRC1 (mannose receptor C-type 1), also known as CD206, is a cell surface receptor primarily expressed on macrophages that plays crucial roles in immune regulation and tissue homeostasis. The protein functions as a cargo receptor mediating endocytosis and transmembrane signaling, with specific binding activity for D-mannose 1. MRC1 serves as a key marker of alternatively activated M2 macrophages, particularly those polarized by IL-4, and is co-expressed with other immunoregulatory markers including CD163, C1q, HLA-DR, and APOE 12. In cancer contexts, MRC1+ macrophages are associated with immunosuppressive tumor microenvironments and poor patient prognosis 32. The receptor is highly expressed in tumor-associated macrophages across multiple cancer types and correlates with T cell exhaustion 3. Additionally, MRC1 has been identified as a potential therapeutic target, as it is expressed on acute myeloid leukemia blasts but not healthy CD34+ stem cells 4. During tissue development and inflammation, MRC1 expression increases during monocyte-to-macrophage differentiation, particularly in the transition to tolerogenic, tissue-resident phenotypes 56. This expression pattern makes MRC1 a valuable marker for studying macrophage polarization and function in health and disease.