Human sDLL-1 comprises the extracellular signaling domain of DLL-1, a member of a structurally-related family of single-pass type I trans-membrane proteins that serve as ligands for Notch receptors. It is expressed in the heart and pancreas, and to a lesser extent in various other tissues. DLL-1 functions to specifically activate the Notch-1 and Notch-2 receptors. The Notch signaling pathway regulates endothelial-cell differentiation, proliferation and apoptosis, and is essential for the development, maintenance and remodeling of the vascular system. DLL-1 suppresses differentiation of hematopoietic progenitor cells into the B-cell lineage while promoting differentiation to T-cell and NK cell precursors. Recombinant human sDLL-1 is a 57.0-6