Interestingly, IL-22 protein levels in the colon tissues from PGRN KO mice were significantly lower than those in WT mice during CDI, which was validated by quantitative real-time PCR analysis showing that IL-22 mRNA levels in colon tissues were also significantly decreased in PGRN KO mice post CDI (supplementary Figure S7a). Here, IL22 is linked to clostridium difficile infection.