A lymphoblastoid cell line, or LCL, is an immortalized population of cells derived from a specific type of white blood cell called a B lymphocyte that scientists around the world began using for biomedical research in the late 1960s. By immortalized, scientists mean that the cells have been altered so they can grow and divide indefinitely, or at least for an extended period of time. That trait of LCLs makes them useful as a replenishable source of cells and the DNA contained within them. Scientists obtain LCLs by first collecting a blood sample and then exposing the B lymphocytes in the blood to Epstein-Barr virus, or EBV. EBV alters the B lymphocytes in such a way that the cells begin to multiply without restraint. Researchers began making and storing LCLs from individuals around the world in the 1960s. As of 2025, LCLs form a mainstay of biomedical research, especially in human genetics and genomics.