Immunology of the gut

The mammalian gut is a major potential site of entry and injury by foreign macromolecules, both microbial and dietary. This symposium discusses the protective mechanisms of the gut immune system, including the nature and functioning of IgA-secreting cells and the role of Peyer's patches, the secretion of IgA in the milk, the development of gut humoral immunity under the impact of bacterial colonization, and immune responses to bacterial plaque. Another immunoglobulin synthesized by the gut is IgE, and a role for it in parasitic infestation seems likely. Eosinophils accumulate in the intestinal wall and are linked to allergic disorder; new clinical evidence suggests that they can injure rather than protect the host. This reverse side of the coin of the immune response is taken up in the second half of the symposium, in which disorders such as chronic inflammatory bowel disease and celiac disease are considered, where mechanisms normally producing immunity may be the cause of tissue damage. The gastrointestinal consequences of primary immunodeficiency are described, together with diseases associated with over-production of immunoglobulins, such as alpha-chain disease, and the further paradox that minor immunodeficiency can show itself in childhood allergy. The mutual interaction of immunology and clinical medicine which this symposium illustrates will make it of interest to many disciplines, including pediatrics, gastroenterology, parasitology, dental surgery, immunopathology, basic immunology and oncology.