A novel monocytoid cultured cell line, P31/Fujioka, derived from acute monoblastic leukemia.

A novel cultured cell line, P31/Fujioka, of monocytoid nature was established from leukemic cells in the peripheral blood of a seven-year-old boy with acute monoblastic leukemia. The P31/Fujioka cells have abundant cytoplasm, an indented nucleus of monocytoid appearance, pseudopods detectable by electron microscopy and alpha-naphthyl butyrate esterase activity which is completely inhibited by NaF, but they have no peroxidase activity. Immunologically, the P31/Fujioka cells possess Fc gamma-receptor and phagocytic activity towards sensitized erythrocytes (oxEAIgG), and are reactive with various monoclonal antibodies such as OKM1, anti-Mol, FMC10, FMC12 and OKI1. Chromosome analysis revealed the presence of marker chromosome 11q--due to Nos. 7; 11 translocation and No. 9 pericentric inversion. These findings indicate that the P31/Fujioka cells are derived from the patient's monoblastic leukemia cells and show a more distinct monocyte antigen than other known monocytoid cultured cell lines, U-937 and THP-1. The absence of Epstein-Barr virus nuclear antigen of this line was confirmed.