Description: The HB7 monoclonal antibody reacts with the human CD38 molecule, an approximately 45 kDa type II transmembrane protein. CD38 is an ectoenzyme which catalyses NAD into nicotinic acid adenine dinucleotide phosphate (NAADP) and cyclic ADP-ribose (cADPR), both of which are secondary messengers. Expression of CD38 is bimodal during B cell development, modulating from high in immature cells to low in intermediate ones and back to high on mature B cells. Additionally CD38 is found in a variety of tissues and other hematopoietic cells (e.g. T cells, NK cells and monocytes) and can be used to phenotype leukemias and monitor HIV-1 progression. The CD34+CD38- population of hematopoietic stems cells is thought to define the most pluripotent cells (e.g. blast colony forming cells). In addition to surface expression, CD38 has recently been found in the nucleus where it may play a role in monitoring calcium levels.