MSR1 (Macrophage Scavenger Receptor 1), also known as SR-A1 or CD204. is a transmembrane glycoprotein primarily expressed on macrophages and dendritic cells. It belongs to the class A scavenger receptor family, characterized by its ability to bind modified low-density lipoproteins (e.g., oxidized LDL) and pathogen-associated molecular patterns. Structurally, MSR1 features a collagen-like domain, a coiled-coil α-helical spacer, and a cysteine-rich C-terminal domain. Its broad ligand specificity enables roles in lipid metabolism, innate immunity, and clearance of cellular debris.
First identified in the 1990s, MSR1 gained attention for its involvement in atherosclerosis through foam cell formation, where macrophages internalize oxidized lipids. However, studies later revealed its dual role in both pro-inflammatory and anti-inflammatory responses, depending on context. It participates in bacterial recognition, apoptotic cell phagocytosis, and modulation of Toll-like receptor signaling.
MSR1 antibodies are valuable tools for studying macrophage biology and disease mechanisms. They are used to detect receptor expression in tissues (e.g., tumor-associated macrophages) and to investigate functional roles in cancer, neurodegenerative diseases, and chronic inflammation. Therapeutic applications are being explored, with some antibodies targeting MSR1 to modulate macrophage activity in tumors or inflammatory disorders. However, challenges remain in understanding isoform-specific functions and ligand-receptor dynamics, as alternative splicing generates multiple MSR1 variants with distinct properties.