The demonstration and function of antibodies in the gastrointestinal tract.

Progress reportThe demonstration and function of antibodies in the gastrointestinal tract The presence of antibody activity in intestinal secretions has been known for 50 years since Davies1 demonstrated specific antibodies in the faeces of patients suffering from dysentery.It is now well documented that the gut of germ-free animals2 and the human neonate3 contains very few plasma cells, and after bacterial contamination the normal complement of plasma cells appears rapidly.These studies have been reviewed recently2.This germ-free condition is associated with absence of immunoglobulin A in the intestinal secretions and the immunoglobulin appears as a response to colonization.The importance of IgA in secretions has been emphasized in reviews by Tomasi and Bienenstock4, by Tomasi and DeCoteau5, and by Heremans6.Work on salivary IgA has been extensively reviewed by Brandtzaeg, Fjel- langer, and Gjeruldsen7.It is the purpose of this review to present recent information on gastro- intestinal antibody production, particularly in the stomach and small intestine, with emphasis on the probable functions of the antibody.There are many technical difficulties in the detection and measurement of antibodies in gastrointestinal secretions.If the gastroenterologist is to maintain a critical understanding of the many relevant papers in this immunological field, then he must appreciate some of the technical problems which are reviewed here.Furthermore, antibody responses within the bowel are important in the study of oral vaccination and some of the relevant experimental work is discussed.The immunological changes in inflammatory bowel disease have been reviewed by Kraft and Kirsner8, and the bowel abnormalities in IgA deficiency are discussed by Bull and Tomasi9.These are not dealt with in the present review. Origin of Intestinal ImmunoglobulinImmunoglobulin may reach the lumen of the gut either by transudation from serum, or as a result of local production and release.There is evidence from studies in animals'0.1'and man'2 that exudation into the gut is a most important route in the catabolism of serum globulins.Currently, however, interest is focused mainly on the local production of immunoglobulin in the tissues of the gut itself.Tissue culture studies show that radioactively labelled amino acids are incorporated into IgG, A, and M by tissues taken from various levels of the gastrointestinal tract'314.Immunofluorescent studies, using fluorescein-labelled antisera specific for the various immuno- globulin classes, have shown the presence of immunoglobulin-containing cells in all gut tissues examined.5-20.The immunoglobulin-containing cells are 483