established 1995 from the pleural effusion of a 30-year-old man with chronic myelogenous leukemia (CML) in T cell lineage blast crisis after bone marrow transplantation; cells carry the Philadelphia chromosome with a e14-a2 (b3-a2) BCR-ABL1 fusion gene. TK6 cells are CD19 positive, 50% of the cell population express CD20 and a small sub-population has been tested positive for CD22. This cell line has been shown to be negative for Bovine Viral Diarrhoea Virus (BVDV).