Junctional Adhesion Molecule B (JAM-B) is a single-pass type I membrane protein that belongs to the juctional adhesion molecules family. JAM-B includes a signal sequence (aa 1-28), an extracellular region (aa 29-238) with one Ig-like C2-type domain and one Ig-like V-type domain, a transmembrane segment (aa 239-259), and a cytoplasmic domain (aa 260 - 298). JAMB is localized to the tight junctions between endothelial cells or epithelial cells. JAM-B is prominently expressed in the heart, placenta, lung, foreskin and lymph node. It is also present on the endothelia of other vessels. JAM-B acts as an adhesive ligand for interacting with a variety of immune cell types and may play a role in lymphocyte homing to secondary lymphoid organs.