EN
Control of parasitic infections is dependent on mechanisms that limit invasion, reproduction or survival of the parasite, including elevated serum IgE, eosinophilia and intestinal mast cell hyperplasia. Studies with mice infected with Heligmosomoides polygyrus, Trichuris muris, Nippostrongylus brasiliensis and Trichinella spiralis have provided considerable information about immune mechanisms correlated with resistance and susceptibility. Activation and cytokine secretion of distinct Th cell subset leads to the generation of effective or ineffective responses resulting in clearance of the parasite load or maintenance of chronic infection. The induction of differential responses remains to be determined but is likely to be influenced at a number of levels including the host genetic background, involvement of accessory cells, activation of co-stimulatory molecules on antigen presenting cells. The regulation of responses to intestinal nematode infections is discussed.