Constitutive Production and Characterization of Interferon-Gamma in a Human T-Lymphoblastoid Cell Line Transformed by a Human Retrovirus

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Abstract
A human T-lymphoblastoid cell line, TCL-Fuj, constitutively produced a large amount of human .gamma.-interferon (IFN) in culture fluids and has sustained stable IFN production for > 2 yr. When cells were incubated in RPMI-1640 medium with 10% fetal calf serum for 3 days, IFN activity was detectable at a cell density of 6 .times. 104 cells/ml; 2000-16,000 U of IFN/ml were produced at 5-10 .times. 105 cells/ml. IFN production was also detected even in serum-free medium and as early as 2 h after cultivation in fresh medium. IFN was inhibited by treatment of cells with either actinomycin D or cycloheximide, indicating the requirement of IFN-mRNA and protein for de novo synthesis. The MW of the IFN was 45,000-60,000 as determined by Sephacryl S200 gel filtration. Two activity peaks corresponding to MW of 22,000 and 39,000 were obtained by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Analysis by isoelectric focusing revealed charge heterogeneity with 4 species at pI [isoelectric point] of 6.0, 7.1, 8.6 and 9.3. Conventional IFN-.gamma. inducers, concanavalin A and 12-O-tetradecanoyl-phorbol-13-acetate, further enhanced the production of IFN in this cell line.