Mucosal defences against orally acquired protozoan parasites, emphasis on Toxoplasma gondii infections.

Protozoan parasites that gain access to the host through the mucosal tissue of the alimentary tract may influence the development of intestinal inflammatory disorders. Despite the diversity of the extracellular and intracellular protozoan pathogens discussed in this review, our current understanding of the mechanisms involved in the immune response indicates that a common exuberant immune response to rid the host of these agents is elicited. This robust inflammatory response is orchestrated both by cells from parenchymatous origin such as intestinal epithelial cells and by cells from the haematopoietic system such as macrophages, dendritic cells and lymphocytes. This inflammatory immune response is controlled by a series of regulatory mechanisms in most species. When this balance is no longer evident, an inflammation of the intestine may occur, leading to acute gastritis and diarrhoea and that would add pathological effects to those because of the pathogen itself.