Hookworm infection is a major cause of disease burden for humans. Recent studies have described hookworm-related immunosuppression in endemic populations and animal models. A Tissue Inhibitor of Metalloproteases (Ac-TMP-1) has been identified as one of the most abundant proteins released by the adult parasite. We investigated the effect of recombinant Ac-TMP-1 on dendritic cell (DC) and T cell function. Splenic T cells from C57BL/6 mice injected with Ac-TMP-1 showed reduced proliferation to restimulation with anti CD3 or bystander antigens such as OVA. Incubation of bone marrow-derived DCs with Ac-TMP-1 decreased MHC Class I and, especially, Class II expression but increased CD86 and IL-10 expression. Co-incubation of splenic T cells with DCs pulsed with Ac-TMP-1 induced their differentiation into CD4+ and, particularly, CD8+ CD25+Foxp3+ T cells that expressed IL-10. These cells were able to suppress proliferation of naïve and activated CD4+ T cells by TGF-Beta-dependent (CD4+ suppressors) or independent (CD8+ suppressors) mechanisms. Priming of DCs with non-hookworm antigens, such as OVA, did not result in the generation of suppressor T cells. These data indicate that Ac-TMP-1 initiates the development of a regulatory response through modifications in DC function and generation of suppressor T cells. This is the first report to propose a role of suppressor CD8+ T cells in gastrointestinal helminthic infections.