Abstract: The present invention provides a method for initiating, promoting and/or directing cell attachment to a matrix or to another cell, comprising contacting an EphB receptor-expressing cell with a tetrameric EphB receptor-binding ligand, whereby binding of the tetrameric ligand promotes multimerization of the EphB receptor, thereby initiating, promoting and directing cell attachment to a matrix or to another cell. Also provided is a method for promoting angiogenesis, comprising contacting EphB receptor-expressing cells which are associated with angiogenesis with a multimeric EphB receptor-binding ligand, whereby binding of the tetrameric ligand promotes multimerization of the EphB receptor, thereby promoting angiogenesis.

Abstract: The present invention provides methods for screening an EphB receptor or an EphB receptor-binding ligand for the ability to promote a selected biological activity when in multimeric form. The invention also provides methods for initiating, promoting, directing, or inhibiting biological activities that involve EphB receptors and/or EphB receptor-binding ligands. The invention further provides compositions that can be used in the foregoing methods.