Immune responses to intestinal parasites: protection, pathology and prophylaxis

Aspects of the immune responses made by hosts to infection with intestinal parasites are discussed in relation to data from experimental systems in mice involving infections with the protozoans Eimeria vermiformis and Cryptosporidium spp., and the nematodes Nippostrongylus brasiliensis and Trichinella spiralis. The focus of the review is our knowledge and understanding of the roles played by the intestinal mucosa and the epithelial cells of the mucosa in the induction, regulation and expression of the immune and inflammatory responses that provide the host with protection but which may also lead to pathology. Emphasis is placed on current knowledge of T helper cell and cytokine involvement in these responses. The relationship between pathology and protection is discussed briefly, as are some aspects of the development of vaccines effective against intestinal parasites.