Human T cell leukemia; established from the peripheral blood of a 4-year-old girl with T cell acute lymphoblastic leukemia (T-ALL) in second relapse in 1977; cell lines BE-13 (DSM ACC 396) and PEER show identical DNA fingerprints and hence share common origin, presumably due to cross-ontamination; however, their diploid and tetraploid karyotypes indicative of earlier and later passage numbers, respectively, suggest that BE-13 is derived from PEER, rather than vice-versa.