Mucosal-Immunity of gastrointestinal tract : immunological interactions of gastrointestinal epithelium

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1.Neutrophil-mesenchymal interactions and the regulation of intestinal epithelial ion secretion. In this model of the intestinal mucosa, intestinal myofibroblasts and subepithelial PMNs release products that directly stimulate intestinal epithelial cells to secrete Cl. In adition,18CO cells appear to enhance PMN-mediated alterations of epithelial secretion. The pro-inflammatory cytokine, IL-1,further augments 18CO-mediated epithelial secretion by inflammatory secretagogues including those released from PMNs. These data suggest that immune-mesenchymal interactions are important in the regulation of intestinal epithelial ion transport.2.We have compared constitutive and stimulated expression of IL-8,MIP-1α,MCP-1,and RANTES in human GI epithelial cell lines following stimulation with PMA and following exposure to S.typhimurium, poliovirus, and respiratory syncytial virus (RSV). IL-8 mRNA and protein was detected in all cell lines tested under basal conditions and both were stimulated by PMA and Salmonella infection. Constitutive and PMA- or Salmonella-stimulated MCP-1 and MIP-1α,were detected by PCR in T84 and Caco-2 but not HT-29 or KATO III. RANTES was expressed in 3 of 4 lines as measured by PCR but protein levels measured in cell supernates were low (except T84). We were unable to detect any effect of Salmonella on the induction of immunoreactive RANTES or MIP-1α. Inoculation of T84 with either poliovirus or RSV increased immunoreactive IL-8,RANTES and MIP-1α. These results suggest that gastrointestinal epithelial cells express a broad range of chemokines which are differentially regulated by bacteria and viruses.