Ephrin‑B3, also known as Elk‑L3, LERK8, Eplg8, NLERK‑2, and EFL6, is an approximately 50 kDa member of the Ephrin‑B family of transmembrane ligands that bind and induce the tyrosine autophosphorylation of Eph receptors. The extracellular domains (ECD) of Ephrin‑B ligands are structurally related to GPI‑anchored Ephrin‑A ligands. Eph‑Ephrin interactions are widely involved in the regulation of cell migration, tissue morphogenesis, and cancer progression. Ephrin‑B3 preferentially interacts with receptors in the EphB family and also with EphA4. The binding of Ephrin‑B3 to Eph proteins also triggers reverse signaling through Ephrin‑B3 (1, 2). Mature human Ephrin‑B3 consists of a 199 amino acid (aa) extracellular domain (ECD), a 21 aa transmembrane segment, and a 93 aa cytoplasmic domain (3, 4). Within the ECD, human Ephrin‑B3 shares 96% and 97% aa sequence identity with mouse and rat Ephrin‑B3, respectively. Ephrin‑B3 is expressed on oligodendrocytes and neurons in the hippocampus and along the midline of the spinal cord (5‑9). It is up‑regulated in glioma and promotes tumor cell invasion and migration (10). Ephrin‑B3 functions as a repulsive axon guidance molecule by inducing growth cone collapse, neurite retraction, and axon pruning (5‑8). Its repulsive effect along the spinal cord midline restricts motor neuron axons to their ipsilateral sides, thereby maintaining the independence of voluntary left side/right side movements (8, 9). Ephrin‑B3 plays a role in the regulation of excitatory synapse density and synaptic maturation (6, 11, 12). It also functions as a cellular receptor for Nipah virus (13) and can induce the migration of memory B cells (14).