The Mrc1 gene (Mannose Receptor C-Type 1) encodes the CD206 protein, a prominent type I transmembrane glycoprotein characterized by multiple carbohydrate-recognition domains. Primarily expressed by macrophages and dendritic cells, particularly those exhibiting an M2-polarized (pro-inflammatory resolution) phenotype, the gene is also active in hepatic sinusoidal endothelial cells and certain barrier tissues ^[1]. The encoded protein functions as a pattern recognition receptor that facilitates the endocytosis of glycoproteins and various pathogens by binding to terminal mannose, fucose, or N-acetylglucosamine residues ^[2]. Beyond its role in innate immunity and pathogen clearance, Mrc1 is a critical marker for identifying perivascular macrophages and interstitial macrophages within the connective tissues of various organs, including the lungs, liver, and dermis ^[3].

Mrc1‑iCre‑tdTomato mice were generated by replacing the TAG stop codon of the mouse Mrc1 gene with the P2A‑iCre‑T2A‑tdTomato expression cassette. When Mrc1‑iCre‑tdTomato mice are crossed with mice containing loxP sites, Cre‑mediated recombination between loxP sites is expected to occur in Mrc1‑positive cells of the offspring.