Regulation of interferon-beta activity by fibroblast cells

Exogenously administered interferons are rapidly cleared from the body. Several pharmacological mechanisms have been implicated in this clearance; however, they do not entirely explain the different clearance rates of the interferons. Cultured cells were studied for their ability to regulate interferon levels in vitro. Preparations of MuIFN-alpha, MuIFN-beta, and MuIFN-gamma were exposed to cells in culture and monitored for any loss in titer. MuIFN-beta titers were found to be significantly reduced following exposure to mouse L-929 fibroblast cells. The reduction of MuIFN-beta activity appeared to be specific for fibroblasts, since the reduction occurred following exposure to L-cells and to mouse embryo fibroblasts, but not to mouse reticuloendothelial cells. Moreover, the ability of the mouse fibroblast cells to reduce MuIFN-beta titers was blocked if the cells were pre-treated with actinomycin D, suggesting that de novo RNA synthesis was required. The titers of IFN-alpha and IFN-gamma were not reduced following exposure to either fibroblast or reticuloendothelial cells. Thus, the reduction of interferon titer by fibroblasts was IFN-beta specific. Similarly, HuIFN-beta titers were reduced following exposure to human fibroblasts. The ability of fibroblast cells to reduce IFN-beta titers was also found to be species-specific, since human fibroblast cells reduced the titer of HuIFN-beta but not MuIFN-beta while murine fibroblasts reduced the titer of MuIFN-beta but not HuIFN-beta. These results suggest that IFN-beta-treated fibroblasts specifically regulate their response to IFN-beta by reducing the titer of the IFN-beta activity.