Local immune mechanisms against parasites

The secretory immunological system of the gastrointestinal tract is associated with the production of secretory IgA immunoglobulins. However, despite the fact that secretory IgA antibodies are known to mediate protection against infection with a number of bacteria and viruses, little information is available on their role in protection against infection with parasites. Thus, although elevated levels of IgA immunoglobulins and antibodies are present in the gastrointestinal tract after infection with a number of helminths and protozoa, conclusive evidence that these are associated with protection against infection is often lacking. However, it has now been demonstrated that intestinal IgA antibodies are associated with protection against infection with Taenia taeniaeformis in mice. In addition, secretory IgA antibodies arising from the common mucosal immunological system of the mammary gland are associated with protection against infection with T. taeniaeformis in mice and rats. Thus, since the portal of entry and site of residence of many parasites is the gastrointestinal tract, the secretory immunological system may act as a first line of defence against infection, and it is possible that oral immunization and local stimulation of the gastrointestinal tract may be effective in inducing protection against infection. The use of nuclear techniques (radioisotope-labelled IgA, autoradiography to follow the role of hepatocytes in IgA transport across the liver) are mentioned marginally only in this review