Cell biological aspects of antibacterial functions of IFNs Type III interferons are emerging as crucial regulators of immunity at barrier sites. Using polarized epithelial cell models, we found that type III interferon treatment tightens the epithelial barrier and protects them against infection with the bacteria Salmonella and Shigella. We wish to determine the cellular mechanisms that enable this protection. We also find that interferons block bacterial infection of epithelial cells in vitro. We are carrying out screens to identify the ISGs responsible for this effect.