Production of interferon-β upon induction with polyinosinic acid:polycytidylic acid during the cell cycle of human fibroblasts

The production of interferon-β was examined at various stages of the cell cycle in synchronized and unsynchronized cell populations induced by poly(I):poly(C). Human fibroblasts were synchronized with mitotic detachment and, at different stages of the cell cycle, poly(I):poly(C) was added for induction of interferon-β. One hour after induction, cell-free medium was collected and assayed for secreted interferon-β. The cells were then fixed and stained with a DNA-specific fluorochrome, 4′,6-diamidino-2-phenylindole (DAPI), for cell cycle analysis by microfluorometry. The data indicated that interferon-β was produced in every stage examined of the cell cycle. In addition, the level of intracellular interferon-β was quantitatively measured in single cells of an unsynchronized cell population using a specific antibody. In the same individual cell, DAPI fluorescence intensity was measured for determination of the cell cycle position. The results show that interferon-β protein can be detected throughout the cell cycle.