The aim of the present study was to investigate the effects of cytokines on intestinal goblet cellsin vitro. For this purpose, we examined the effects of recombinant interferon gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α) on the human colonic goblet cell line Cl.16E by morphological and kinetic studies, and by the assessment of mucus production during IFN-γ/TNF-α treatment. Control cultures of Cl.16E cells grown on nitrocellulose filters formed monolayers of polarized goblet cells, which had kinetic characteristics similar to those of a differentiated epithelium in steady state. The combined action of IFN-γ and TNF-α caused a dose-related cellular exfoliation, leading to the formation of a mucoid cap made of mucus and cellular debris. The remaining viable cells underlying the mucoid cap were cuboidal and devoid of mucus granules. A dose-related increase in cellular incorporation of [³H]thymidine was reactive to the cytokine-induced cell loss. The synergistic effects of IFN-γ and TNF-α were found to be reversible when the cells were reincubated in a culture medium without cytokines. Furthermore, 5-aminosalicylic acid partially protected Cl.16E cells against cellular injury caused by IFN-γ and TNF-α. On the whole, these morphological and kinetic findings argue that the changes induced in Cl.16E cells by IFN-γ and TNF-α closely parallel those observed during the acute phase of ulcerative colitis, and show that these cytokines can regulate intestinal mucus production by modulating cellular exfoliation, thus leading probably to a reinforced protection of the damaged mucosa.