Ephrin receptors bind members of the ephrin ligand family. They are divided into 2 groups based on the similarity of their extracellular domain sequences and their affinities for binding ephrin-A and ephrin-B ligands. They make up the largest subgroup of the receptor tyrosine kinase (RTK) family. Eph receptor B1 (EphB1) and Eph receptor B2 (EphB2) are receptors for ephrin-B family members. Developing and adult neural tissue express nearly all of the Ephrin receptors and ephrin ligands. Ephrins and ephrin receptors also play a significant role in angiogenesis. EphB2 acts as a tumor suppressor.