Description: The HMD1-5 monoclonal antibody reacts with mouse Delta-like 1, one of five type I transmembrane proteins that serves as a Notch receptor ligand. Upon binding the Notch receptor (e.g. Notch 1-4), Delta-like 1 undergoes proteolytic cleavage, first by ADAM-family metalloproteases and then by γ-secretase. The second cleavage event releases an intracellular fragment whose biological function remains controversial. Delta-like 1 is expressed by thymic stromal cells, as well as on macrophages, dendritic cells, and stromal cells in the spleen. This protein is also expressed in nonhematopoietic tissues such as the lung and brain. Delta-like 1 has been linked to B cell development and differentiation, especially marginal zone and plasma cells, regulation of splenic dendritic cells, and leukemogenesis.