T-CELL-MONOCYTE INTERACTIONS REGULATE EPITHELIAL PHYSIOLOGY IN A COCULTURE MODEL OF INFLAMMATION

We have examined the effect of T cell activation, with or without mono cytes, on epithelial electrolyte transport and barrier functions. Conf luent monolayers of human T84 epithelial cells were cocultured (1-3 da ys) with peripheral blood mononuclear cells (PBM) or T cells activated by anti-CD3 antibody. Monolayers were then mounted in Ussing chambers , and changes in ion transport (indicated by short-circuit current, I- sc) and barrier (indicated by resistance and radiolabeled probe fluxes ) functions were assessed. Coculture with activated PBM or conditioned medium from these cells altered the transport (decreased I-sc respons es to carbachol and forskolin) and barrier (decreased resistance and i ncreased fluxes of [H-3]mannitol and Cr-51-EDTA) properties of T84 mon olayers. In contrast, coculture with equal numbers of T cells activate d in the absence of monocytes did not significantly affect epithelial physiology. Monocytes treated with conditioned media from activated T cells evoked epithelial abnormalities similar to those caused by cultu re with activated PBM. Total correction of epithelial abnormalities wa s achieved only by treating T cell-conditioned medium with anti-interf eron-gamma (IFN-gamma) before addition to monocytes, as well as additi on of anti-tumor necrosis factor-alpha (TNF-alpha) to the coculture. E xogenous recombinant IFN-gamma and TNF-alpha added to T84 monolayers d id not mimic the physiological changes induced by immune cells; additi on of these cytokines to monocytes did reproduce the effects. We concl ude that T cell-derived IFN-gamma activates monocytes to release TNF-a lpha and other soluble mediators, resulting in epithelial dysfunction.