CD38, a transmembrane glycoprotein, belongs to the ADP-ribosyl cyclase family, possessing dual biological functions: it serves as a key enzyme for intracellular calcium signaling and acts as a cell surface receptor involved in signal transduction. It is widely distributed in B cells, T cells, myeloid cells, and some non-immune cells such as neurons and muscle cells. CD38 catalyzes the generation of cADPR and ADPR from NAD+, crucially regulating calcium ion release and cellular functions, including proliferation, differentiation, and migration. Its gene expression patterns and mutations are closely associated with autoimmune diseases, chronic lymphocytic leukemia, and other cancers, making it a key target for researching and treating immune-related diseases.