The epidermal growth factor (EGF)-TM7 family constitutes a group of class B G-protein coupled receptors, which includes CD97, EMR1 (EGF-like molecule containing mucin-like hormone receptor 1, designated F4 80 in mouse), EMR2, EMR3, FIRE, and ETL (1a3). These family members are characterized by an extended extracellular region with several N-terminal EGF domains, and are predominantly expressed on cells of the immune system (1a3). The EGF-TM7 protein family are encoded by a gene cluster on human chromosome 19p13 (1,3,4). The F4 80 molecule is solely expressed on the surface of macrophages and serves as a marker for mature macrophage tissues, including Kupffer cells in liver, splenic red pulp macrophages, brain microglia, gut lamina propria, and Langerhans cells in the skin (1). F4 80 EMR1 undergoes extensive N-linked glycosylation as well as some O-linked glycosylation (5,6). The function of F4 80 EMR1 is unclear, but it is speculated to be involved in macrophage adhesion events, cell migration, or as a G-protein coupled signaling component of macrophages.
