Folate receptor beta (FOLR2, also known as FR-β) is a glycosylphosphatidylinositol (GPI)-anchored cell surface folate-binding protein that mediates high-affinity uptake of reduced folates and folate conjugates. In mice, Folr2 is predominantly expressed in subsets of tissue-resident macrophages and monocyte/macrophage-lineage cells, rather than in most epithelial compartments. It is particularly enriched in alternatively activated (M2-like) macrophages, tumor-associated macrophages (TAMs), and macrophage populations associated with tissue remodeling, immune regulation, and chronic inflammation. Through facilitating folate internalization and reflecting a specialized macrophage activation state, FOLR2 is widely used as a marker for immunoregulatory macrophages in contexts such as tumor microenvironment, fibrosis, wound healing, and inflammatory disease.