Immunoglobulin superfamily member 3 (IGSF3), also known as Glu-Trp-Ile EWI motif-containing protein 3, IgSF3 and EWI-3 and IGSF3, is a single-pass type I membrane protein that belongs to the EWI subfamily of the Ig superfamily of molecules. IGSF3 has an overall structural similarity and strong sequence similarity to V7, a human leukocyte surface protein. IGSF3 contains eight Ig-like C2-type (immunoglobulin-like) domains. IGSF3 is expressed in a wide range of tissues with high expression in the placenta, kidney, and lung. EWI-2 is part of a novel Ig subfamily that includes EWI-F (F2alpha receptor regulatory protein (FPRP), CD9P-1 ), EWI-3 (IGSF3), and EWI-101 (CD101). All four members of this Ig subfamily contain a Glu-Trp-Ile (EWI) motif not seen in other Ig proteins. Human IGSF3 shares 92 % aa identity with mouse IGSF3.