AIM: To investigate the role of Peyer’s patch lymphocytesin the regulation of enteric epithelial barrier and ion transportfunction in homeostasis and host defense.METHODS: Mouse Peyer’s patch lymphocytes were co-cultured with human intestinal epithelial cell line Caco-2either in the mixed or separated (isolated but permeablecompartments) culture configuration.Barrier and transportfunctions of the Caco-2 epithelial monolayers were measuredwith short-circuit current (Isc) technique.Release of cytokineswas measured by enzyme-linked immunosorbent assay(ELISA) and cytokine mRNA expression was analyzed bysemi-quantitative RT-PCR.Barrier and iontransport functionsof both culture conditions following exposure to Shigellalipopolysaccharide (LPS) were also examined.RESULTS: The transepithelial resistance (TER) of the epithelialmonolayers co-cultured with Peyer’s patch lymphocyteswas maintained whereas that of the Caco-2 monolayersalone significantly decreased after eight days in culture.The forskolin-induced anion secretion,in either absenceor presence of LPS,was significantly suppressed in theboth co-cultures as compared with the Caco-2 cells alone.Furthermore,only the mixed co-culture condition inducedthe expression and release of rnIL-6 from Peyer’s patchlymphocytes,which could be further enhanced by LPS.However,both co-culture conditions suppressed expressionand release of epithelial hIL-8 under the unstimulatedconditions,while the treatment with LPS stimulated theirhIL-8 expression and release.CONCLUSION: Peyer’s patch lymphooltes may modulateintestinal epithelial barrier and ion transport function inhomeostasis and host defense via cell-cell contact andcytokine signaling. AIM: To investigate the role of Peyer’s patch lymphocytes in the regulation of enteric epithelial barrier and ion transportfunction in homeostasis and host defense. METHODS: Mouse Peyer’s patch lymphocytes were co-cultured with human intestinal epithelial cell line Caco-2either in the mixed or separated ( isolated but permeablecompartments) culture configuration. Barrier and transportfunctions of the Caco-2 epithelial monolayers were measured with short-circuit current (Isc) technique. Release of cytokines was measured by enzyme-linked immunosorbent assay (ELISA) and cytokine mRNA expression was analyzed by semi-quantitative RT-PCR. Barrier and iontransport functions of both culture conditions following exposure to Shigella lipopolysaccharide (LPS) were also observed .RESULTS: The transepithelial resistance (TER) of the epithelialmonolayers co-cultured with Peyer’s patch lymphocyteswas maintained but that of the Caco-2 monolayersalone decreased after eight days in culture.The fors kolin-induced anion secretion, in either absence absence presence of LPS, was significantly suppressed in theboth co-cultures as compared with the Caco-2 cells alone. Durthermore, only the mixed co-culture condition induced the expression and release of rnIL-6 from Peyer’s patchlymphocytes, which could be further enhanced by LPS. Although, both co-culture conditions suppressed expression and release of epithelial hIL-8 under the unstimulated conditions, while the treatment with LPS stimulated their hIL-8 expression and release. CONCLUSION: Peyer’s patch lymphomates may modulate intestinal epithelial barrier and ion transport function in homeostasis and host defense via cell-cell contact andcytokine signaling.