CD38, also known as ADP Ribosyl Cyclase 1, is a transmembrane glycoprotein that functions as both a receptor and an ectoenzyme involved in cell adhesion, signal transduction, and calcium signaling. It is normally expressed on plasma cells, activated T and B
lymphocytes, natural killer (NK) cells, and some myeloid cells.
CD38 is especially important in multiple myeloma, where it is strongly expressed on malignant plasma cells. It is also relevant in chronic lymphocytic leukemia.