AIM: To determine the immunomodulatory effect of Shiitake (a mushroom extract),we tested its effect on liver-mediated immune regulation in a model of immune-mediated colitis.METHODS: Four groups of mice were studied.Colitis was induced by intracolonic instillation of TNBS in groups A and B.Groups A and C were treated daily with Shiitake extract,while groups B and D received bovine serum albumin.Mice were evaluated for development of macroscopic and microscopic.The immune effects of Shiitakke were determined by FACS analysis of intra-hepatic and intrasplenic lymphocytes and IFN-γ ELISPOT assay.RESULTS: Administration of Shiitake resulted in marked alleviation of colitis,manifested by significant improvement in the macroscopic and microscopic scores,and by reduction in IFN-γ-producing colonies in group A,compared to group B mice (1.5 pfu/mL vs 3.7 pfu/mL,respectively).This beneficial effect was associated with a significant increase in the intrahepatic CD8+ lymphocyte trapping,demonstrated by an increased intrasplenic/intrahepatic CD4/CD8 lymphocyte ratio.These effects were accompanied by a 17% increase in the number of intrahepatic natural killer T (NKT) cells.A similar effect was observed when Shiitake was administered to animals without disease induction.CONCLUSION: Shiitake extract affected livermediated immune regulation by altering the NKT lymphocyte distribution and increasing intrahepatic CD8+ T lymphocyte trapping,thereby leading to alleviation of immune-mediated colitis.