Helminth parasites are of considerable medical and economic importance. Studies of the immune
response against helminths are of great interest in understanding interactions between the host immune system
and parasites. The lack of exposure to helminth infections, as a result of improved living standards and medical
conditions, may have contributed to the increased incidence of inflammatory bowel diseases (IBDs) in the
developed world. Epidemiological, experimental, and clinical data sustain the idea that helminths could provide
protection against IBD. Studies investigating the underlying mechanisms by which helminths might induce such
protection have revealed the importance of regulatory pathways, for example, regulatory T-cells. Further
investigation on how helminths influence both innate and adaptive immune reactions will shed more light on the
complex pathways used by helminths to regulate the hosts immune system. Although therapy with living
helminths appears to be effective in several immunological diseases, the disadvantages of a treatment based on
living parasites are explicit. Therefore, the identification and characterization of helminth-derived
immunomodulatory molecules that contribute to the protective effect could lead to new therapeutic approaches
in IBD and other immune diseases.