Keywords
Abstract
Among the immune formations of the digestive system, lymphoid nodules (Peyer's patches) of the small intestine play an exceptional role. They, like the thymus, tonsil, appendix of mammals, belong to the lymphoepithelial organs in which lymphopoiesis occurs and are in close interaction with the reticular tissue, the epithelium. In birds, the thymus and the bursa of Fabricius are the primary organs of lymphopoiesis, in which T- and B-lymphocytes differentiate, respectively. In mammals, an analogue of the bursa of Fabricius has not been found, although some authors consider the appendix and Peyer's patch as such. The basis for such assumptions may be their topographic location - the digestive tract, as well as their location on the antimesenteric side, in contact with the epithelium. The jejunum is a section of the small intestine, which occupies an intermediate position between the duodenum and the ileum, and from morphological positions it reflects the basic principle of the structure, being the most functionally active section, especially the proximal part. The multifunctionality of the small intestine allows it to participate in many processes determined by immune responses that induce restoration, protection, and radioresistance. It was lymphocytes that received the status of the main cells that provide the immune process and the specificity of immune reactions.