Evidence from epidemiological studies indicates an inverse correlation between the incidence of certain immune-mediated diseases,including inflammatory bowel diseases(IBD),and exposure to helminths.Helminth parasites are the classic inducers of Th2 responses.The Th2-polarized T cell response driven by helminth infection has been linked to the attenuation of some damaging Th1 driven inflammatory responses,preventing some Th1-mediated autoimmune diseases in the host,including experimentally induced colitis.Helminth parasites(the porcine whipworm,Trichurissuis)have been tested for treating IBD patients,resulting in clinical amelioration of the disease.As a result,there is a great deal of interest in the research community in exploring the therapeutic use of helminth parasites for the control of immune-mediated diseases,including IBD.However,recent studies have provided evidence indicating the exacerbating effects of helminths on bacterial as well as non-infectious colitis in animal models.Therefore,a better understanding of mechanisms by which helminths modulate host immune responses in the gut may reveal novel,more effective and safer approaches to helminth-based therapy of IBD.(C)2008 The WJG Press.All rights reserved.