CLDN2 and inflammatory bowel disease: Claudin-2 is a cation pore-forming member of the claudin family of transmembrane proteins that is frequently elevated during inflammation, including in IBD, while during bacterial infection its expression is increased as part of a host-protective mechanism.35,36 Consistent with our previous studies, claudin-2 levels were significantly elevated in Ptpn2∆IEC mice compared to the Ptpn2fl/fl- PBS treated littermates, while a similar, albeit not statistically significant, effect was observed in the K12 infected Ptpn2∆IEC mice (Figure 3(B,E)).