Interleukin 6 (IL-6), oncostatin M (OSM) and leukaemia-inhibitory factor (LIF) share a common signal-transducing subunit in each of their receptors and thus mediate an overlapping spectrum of biological activities. Although all of these cytokines stimulate the production of alpha1-proteinase inhibitor (alpha1-PI) in hepatocyte-derived cells, only OSM is able to up-regulate levels of this inhibitor in epithelial cells originating from the lung. In this study we characterized human lung-derived epithelial-like HTB58 cells for their ability to synthesize alpha1-PI after treatment with IL-6, OSM and LIF. The results demonstrate that the resistance of HTB58 cells to the effects of IL-6 and LIF was not because of a lack of their individual functional receptors and suggest that OSM utilizes two different receptors, gp130/LIF receptor and gp130/OSM receptor, in lung-derived epithelial cells.