Tight Junctions and CellCell Interactions

Chronic inflammation in mucosal tissues can influence epithelial barrier function via proinflammatory cytokines such as interferon (IFN)-γ and tumor necrosis factor-α. Increased mucosal levels of these cytokines have been observed in mucosal biopsies from patients with a chronic inflammatory condition referred to as inflammatory bowel disease. Paracellular permeability across epithelial cells is regulated by tight junctions (TJs ), which are the apical most junctions in epithelial cells. Given that pro-inflammatory cytokines modulate the epithelial barrier and that TJs regulate epithelial permeability, we analyzed the influence of IFN-γ on TJ function/structure. Our results suggest that IFN-γ induced a time-dependent increase in paracellular permeability that was associated with internalization of TJ transmembrane proteins, occludin, junction adhesion molecule A, and claudin-1. In this chapter, we focus on selected methods used to investigate the influence of IFN-? on epithelial barrier function.