FOLR2 (folate receptor beta) is a cell surface protein that was originally thought to be specific for placenta, but it can be also expressed in other tissues, including hematopoietic cells. Its expression is increased in malignant tissues. FOLR2 may play a role in the transport of methotrexate in synovial macrophages in rheumatoid arthritis patients. FOLR2 is a marker for macrophages generated in the presence of M-CSF (M2), including M2-like tumor-associated macrophages, which exert potent immunosuppressive functions within the tumor environment, but not GM-CSF (M1), and whose expression correlates with increased folate uptake ability.
