CD38 is a glycoprotein found on the surface of many immune cells (white blood cells), including CD4+, CD8+, B lymphocytes and natural killer cells. CD38 also functions in cell adhesion, signal transduction and calcium signaling. CD38 is a multifunctional ectoenzyme that catalyzes the synthesis and hydrolysis of cyclic ADP-ribose (cADPR) from NAD+ to ADP-ribose in addition to synthesis of NAADP from NADP+. The loss of CD38 function is associated with impaired immune responses, metabolic disturbances, and behavioral modifications including social amnesia possibly related to autism.