Observing the quantitative and qualitative composition of immunocompetent cell populations of the lymphoid tissue of the immunogenic organs allows to determine the immune status of the organism in a certain age period. The object of research is determing the cellular composition of the lymphoid tissue of the cecal Peyer’s patches and cecal (apical) diverticula in ducks in age-concerned aspect. Material simples for research were selected from broiler ducks of the Blagovarsky cross. Cytological testss were performed on imprint specimens. Immunoblasts, lymphocytes, proplasmocytes, and plasmocytes, monocytes, and macrophages are distinguished among the cells of the lymphoid tissue of the cecal Peyer’s patches and the cecal diverticula. The content of these cells is not the same. Population of lymphocytes in imprint specimens is the biggest. It consists of subpopulations of small, medium, and large lymphocytes, the ratio is uneven. The largest is a subpopulation of small lymphocytes, and the smallest is a subpopulation of large ones. The total content of lymphocyte in cecal Peyer’s patches and cecal diverticula decreases with age of the subject ducks. The content of small and medium-sized lymphocytes in the cecal diverticula and small lymphocytes in the cecal Peyer’s patches as well decreases. Simultaneously, the content of large lymphocytes in the cecal diverticula, large and medium lymphocytes in the cecal Peyer’s patches increases. The immunoblasts content in the lymphoid tissue of the studied immune formations decreases with age of ducks, while the quantity of macrophages and monocytes conversely increases. Proplasmocytes and plasmocytes are detected in the lymphoid tissue of cecal Peyer’s patches and cecal diverticula from the age of 10 days in ducks. Their content increases significantly with the poultry age. Reticular cells observation if complicated due to their location under a dense layer of lymphoid cells. Fibroblasts, M-cells, erythrocytes, and granulocytes in imprint specimens are detected in trace amounts. The established changes in the cellular composition of the lymphoid tissue of the cecal Peyer’s patches and the cecal diverticula in ducks in the age-related aspect confirm the occurring immune reactions within them. Consideration of these changes will improve the effectiveness of anti-epizootic measures

Immune formations of birds' digestive organs, including the esophageal tonsil and Meckel’s diverticulum, protect the body from foreign antigens that enter the body with food and water and play an important role in maintaining the genetic constancy of its internal environment. This unique property of the immune system is formed during ontogenesis and is associated with maintaining the selection of lymphocyte clones that are able to respond to foreign antigens and carry out a specific immune response of two types: humoral and cellular. This article presents the results of a study of T- and B-lymphocyte subpopulations of the esophageal tonsil of Shever 579 cross chickens at the age of 25, 180 and 300 days, the Meckel diverticulum of the Blagovarsky cross ducks at the age of 30, 150 and 180 days. Immunohistochemical and statistical research methods were used to determine the localization and quantitative parameters of cell populations of lymphocytes (CD4+, CD8+, CD20+) using monoclonal antibodies and the DAKO EnVision FLEX+ imaging system (Dako Cytomation, Denmark). Separate subpopulations of T-lymphocytes (CD4+ - helpers, CD8+ -cytotoxic / T-suppressors) and mature B-lymphocytes (CD20+) were found in the esophageal tonsil and Meckel diverticulum of birds. Their presence confirms that antigen-independent proliferation and differentiation of lymphocytes into effector cells occur in the immune formations of the digestive system. The lymphoid tissue of these formations is represented mainly by a well-defined diffuse form and nodules with light centers (secondary). In the esophageal tonsil of chickens, these structures are located in the tunica mucosa and tela submucosa, and in the Meckel diverticulum of ducks – also in the tunica muscularis. The content of lymphocytes with these markers predominates in diffuse lymphoid tissue compared to that in secondary lymphoid nodules. In the diffuse lymphoid tissue of the esophageal tonsil, lymphocytes are located mainly near the adenomeres and excretory ducts of the esophageal glands, blood vessels, and under the surface epithelium, and in Meckel’s diverticulum – around the crypts, in their epithelium and in the epithelium of the villi. They are also found in the light centers of lymphoid nodules and on their periphery. The indices of the content of lymphocytes with the indicated markers in the esophageal tonsil and Meckel diverticulum which we determined were associated with age characteristics of the poultry in the postnatal period of ontogenesis. According to our observations, the content of CD20+ lymphocytes was the highest, while the populations of CD4+ and CD8+ lymphocytes were much smaller. This indicates an increase in the activity and predominance of the humoral immunity over the cellular one. The content of CD20+ lymphocytes was highest in birds at the age of 180 days, that is, during their sexual maturity. The data presented in the work can be used by morphologists researching the organs of the immune system, immunologists, poultry specialists involved in breeding, using and raising poultry and in educational work.

The article presents the results of histological studies of topography, microstructure and functional features of the stomach lymphoid tissue in birds. The research was carried out on 12 species of wild birds belonging to 6 orders. Classical methods of histological specimens staining with hematoxylin and eosin, according to Weigert, Van Gieson, and argentum nitrate impregnation according to Kelemen were used when performing the work. It has been confirmed that the birds' stomach has glandular (proventriculus), muscular (ventriculus, gizzard) and pyloric parts, which are not equally expressed in separate species. In all parts of the stomach, lymphoid tissue is represented by local clusters, which in birds of the orders Galliiformes (P. colchicus, B. bonasia, P. crictatus); Anseriformes (B. canadensis); Passeriformes (P. pica, C. cornix); Gruiformes (G. chloropus, F. atra); Ciconiiformes (C. ciconia) and Columbiiformes (C. livia) are located in the tunica mucosa and submucosa, and in B. canadensis, F. atra, G. chloropus also in the tunica muscularis and tunica serosa. In L. lagopus and G. glandarius, lymphoid tissue has been found only in the proventriculus and its intermediate zone. Structural levels of lymphoid tissue (diffuse form, prenodules, primary and secondary lymphoid nodules) are unequally expressed in the birds' stomach. In B. bonasia, B. canadensis, P. pica, C. cornix, C. ciconia, C. livia, only a diffuse form appears in all its parts. This form of lymphoid tissue is registered in the ventriculus of other birds species and proventriculus in L. lagopus and G. glandarius. All levels of the lymphoid tissue structural organization are detected in the proventriculus in P. crictatus, G. chloropus and in the proventriculus and pyloric part of the stomach in P. colchicus and F. atra. The content of lymphoid tissue is different in parts of the birds' stomach. Most of all it is contained in the intermediate zone of the proventriculus and the pyloric part of the stomach. Diffuse form is the most common among the levels of lymphoid tissue structural organization. The research results make it possible to more fully assess the morphofunctional status of wild birds and, accordingly, to find out the state of their immune system

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The structure and topography of the Bursa of Fabricius (BF) differs from other central immune organs. Structural components, providing BF function are located in mucosa, which is constantly influenced by antigen stimulation. Therefore the reports, which have appeared recently, indicate that BF may function as a peripheral immune organ. The latter is known to be situated in the alimentary canal mucosa (caecal tonsils, Peyer's patches) and possess peculiar epithelium. The aim of our study was to investigate the structure and cell composition of BF epithelium in chicken, turkey, quails, ducks and pigeons using light and electronic microscopy. The studies have shown that epithelium overlying BF folds is pseudostratified columnar, but between them and in their base it might be cuboidal or columnar. Pseudostratified epithelium consists of columnar cells with a few microvilli on their apical surface, goblet cells, infrequent endocrine cells and macrophages. BF epithelium is spongious due to its infiltration by lymphoid cells. The large quantity of the latter is found in subepithelial connective tissue. Infiltration by lymphoid cells is considered to be typical for the alimentary tract mucosa, where the aggregated lymphoid nodules are situated. Thus, our study supports the thoughts that BF may have function of central and peripheral immune organ.