Accordingly, IL-22-treated PGRN KO mice had reduced gut permeability as quantified by FITC-dextran gut-barrier permeability assay (Figure 5f), and increased protein levels of Occludin were observed in the colon tissues from PGRN KO mice treated with IL-22 when compared with PBS-treated PGRN KO mice post CDI (Figure 5g). Here, OCLN is linked to clostridium difficile infection.