Lysis of pulmonary fibroblasts by lymphokine (IL-2)-activated killer cells—a mechanism affecting the human lung microenvironment?

In this study we investigated whether IL-2-activated killer cells may bind and exert lytic activity against non-transformed lung fibroblasts. We demonstrated that human lymphokine-activated killer (LAK) cells generated in vitro following incubation with recombinant IL-2 of either peripheral blood mononuclear cells (PB-LAK) or lymphocytes obtained from bronchoalveolar lavage (BAL-LAK), but not resting cells, can lyse normal lung fibroblasts obtained from transbronchial lung biopsies in a 4-h ⁵¹Cr release assay. Both autologous and allogeneic fibroblasts were consistently lysed by LAK cells, thus suggesting that the phenomenon we observed is not MHC-restricted. Since fibroblasts can bind IL-2 through specific receptors, we evaluated whether long-term culture with rIL-2 could modulate the susceptibility to lysis of target cells. Our data showed that autologous fibroblasts were more resistant to lysis than allogeneic fibroblasts when they were cultured with rIL-2. Since LAK cells have been demonstrated to release a series of different immunomodulatory cytokines, we evaluated the effect of short-term incubation of fibroblasts with different factors, including IL-1, IL-2, IL-3, IL-4, IL-6, tumour necrosis factor-alpha (TNF-α), and interferon-gamma (IFN-γ), on the binding and the lysis mediated by LAK cells. These cytokines were not directly cytotoxic on fibroblasts. Only IFN-γ was found to have a significant protective effect against the lysis. Our data support the concept that a self-directed cytotoxicity against pulmonary fibroblasts is generated during lymphocyte activation with rIL-2.