MOLT-4 is a T lymphoblast cell line derived from the peripheral blood of a 19-year-old male patient with Acute lymphoblastic leukemia (ALL) in relapse in 1971. It is a sister cell line of MOLT-3, while MOLT-4 shows an unusual T-cell antigen receptor gamma-chain gene (T-gamma) rearrangement. MOLT-4 cells have a doubling time of around 30 hours, grow in suspension, and are tumorigenic in untreated nude mice, anti-lymphocyte serum-treated mice, and x-irradiated mice. MOLT-4 cells have a hypertetraploid chromosome number with the modal chromosome number of 95 occurring in 24% of cells but show stable and recurrent structural abnormalities of chromosomes and longer telomere length. MOLT-4 expresses a variety of T cell markers including CD1, CD2, CD3A, CD3B, CD3C, CD4, CD5, CD6, and CD7. They also express high levels of terminal deoxynucleotidyl transferase (TdT). The MOLT-4 cell line does not produce immunoglobulin or Epstein-Barr virus. The patient from whom the cells were derived had received prior multidrug chemotherapy. There is a G -> A mutation at codon 248 of the p53 gene, and P53 is not expressed. The line was initially contaminated with mycoplasma but has since been cured with antibiotics.