DLL1 and bacterial infectious disease: Delta-like canonical Notch ligand 1 (DLL1), a transmembrane protein of the Delta/Jagged family and ligand of Notch receptors, was found to be upregulated in primary human monocytes in response to an in vitro bacterial infection [10], subsequently resulting in high concentrations of its cleavage product, soluble DLL1 in the cell supernatant.