Cell surface transmembrane ligand for Eph receptors, a family of receptor tyrosine kinases which are crucial for migration, repulsion and adhesion during neuronal, vascular and epithelial development (PubMed:7973638, PubMed:8070404). Binding to Eph receptors residing on adjacent cells leads to contact-dependent bidirectional signaling into neighboring cells (PubMed:7973638, PubMed:8070404). Shows high affinity for the receptor tyrosine kinase EPHB1/ELK (PubMed:7973638, PubMed:8070404). Can also bind EPHB2 and EPHB3 (PubMed:8070404). Binds to, and induces collapse of, commissural axons/growth cones in vitro (By similarity). May play a role in constraining the orientation of longitudinally projecting axons (By similarity). {ECO:0000250|UniProtKB:P52795, ECO:0000269|PubMed:7973638, ECO:0000269|PubMed:8070404}. This is the function of EFNB1 (ephrin B1, ENSG00000090776).