GC-C is essential to maintain intestinal barrier function during C. rodentium infection. A: GC-C+/+ and GC-C−/− mice were given a FITC-dextran tracer by oral gavage on day 4 p.i. and serum fluorescence was measured four hours later. Relative to naïve mice as well as infected GC-C+/+ animals, GC-C−/− mice have a substantial and significant increase in tracer movement from the gut lumen into the blood indicating a loss of intestinal barrier function. (*P ≤ 0.05; n = 4 – 8 mice per group). B: Immunofluorescent staining of claudin 2 or claudin 3 (green) with E-cadherin (red) and DAPI (blue) counter stains reveals no apparent differences between infected control and GC-C−/− mice at day 4 p.i. C: Immunoblotting of claudin 2 and claudin 3 shows similar protein levels in extracts from distal colon of mice infected by C. rodentium for 4 days. βTubulin is shown to demonstrate equal loading.