F4/80 also known as Adhesion G protein-coupled receptor E1 (ADGRE1), is a surface receptor with seven transmembrane segments that belong to the EGF-7-transmembrane family of G protein-coupled receptors . EMR1 expression is restricted to eosinophilic granulocytes, where expression is overlapping with the eotaxin receptor CCR3 and the immunoglobulin-like lectin Siglec-8. Absence on other leukocytes, including basophils, implies that EMR1 is a highly specific marker for eosinophils in humans and may be used as a novel therapeutic target for eosinophilic disorders . F4/80, the murine homolog of EMR1, is a marker of murine macrophage. The apparent molecular weight of F4/80 is 160 kDa, which is larger than the calculated molecular weight due to post-translational modifications .