Isolation of Daudi cells with reduced sensitivity to interferon. I. Characterization

Treatment of Daudi cells with successively increasing concentrations of interferon-alpha resulted in the selection of a cell population which multiplied in the continued presence of 10(4) units/ml of interferon-alpha. A number of clones of interferon-resistant Daudi cells were isolated from this population. Two clones, DIF2 and DIF3, were found to exhibit moderate and pronounced resistance, respectively, to both the antiviral and antiproliferative actions of human interferons-alpha and -beta. These clones were also less responsive to the enhancement by interferon of Epstein-Barr virus early antigen expression. Both the surface antigens and karyotype of the interferon-resistant clones were similar to those of parental Daudi cells. After prolonged cultivation in the absence of interferon, DIF3 cells were found to 'revert' to an intermediate interferon sensitivity. The interferon sensitivity of clone DIF2 remained unchanged even after more than 1 year in culture.