The Notch receptors and their ligands are highly conserved from invertebrates to mammals. The Delta-like 1 (DLL1) is one of the four or five Notch ligands identified. The binding to Notch receptor results in the proteolysis of Notch and movement of intracellular portion of Notch into the nucleus.This translocation triggers a series of signaling process. Delta-like 1 is reported to be essential for the maintenance of marginal zone B cells in normal mice, and engagement of Notch 1 by DLL1 promotes differentiation of B lymphocytes to antibody-secreting cells.