Quantification and description of gut-associated lymphoid tissue in, shabbout, Arabibarbus grypus (Actinopterygii: Cypriniformes: Cyprinidae), in warm and cold season

Abstract

Background. Gut-associated lymphoid tissue (GALT), is a primary lymphoid tissue and a part of the mucosal lymphoid system. Depending on the location, it present as aggregations of lymphoid cells. There are several reports of structural differences in the lymphoid tissue attached to the gastrointestinal tract between different species of fish, as well as different areas of the gastrointestinal tract of a fish in the cold and warm seasons. Identifying and expressing these differences in terms of tissue structure, in addition to diagnosing aquatic diseases, is also of particular importance for vaccination and disease control. Materials and methods. For this purpose, after collecting the desired samples routine histological procedure was performed and 4–6 µm sections were obtained and were subsequently stained with hematoxylin-eosin, periodic acid–Schiff, and TUNEL immunohistochemical staining method. Results. The results showed that four main layers, i.e., tunica mucosa, tunica submucosa, tunica muscularis, and tunica serosa, were observed in the wall of the gut of Arabibarbus grypus (Heckel, 1843), as had been observed in other teleosts. GALT was seen in two different shapes in two areas. The former consisted of intra-epithelial scattered cells, which were arranged in the pillar structures and extended to the upper regions of the epithelium, but were more concentrated in the mid bases. The latter was found in lamina propria and submucosa regions. In the lamina propria, they had a strip-shaped arrangement and were placed in several rows below the base membrane, but in the submucosa, they were scattered and less densely packed. Micrometric results showed that not only the distribution of the lymphocytic cells in the intestine of both male and female specimens varied in different areas but also in some areas, the difference was statistically significant in both cold and warm seasons (P < 0.05). TUNEL immunohistochemical staining revealed that the number of apoptotic cells in both sexes was more in the anterior part of the intestinal bulb and in the posterior part of the proper intestine in the warm season compared to the cold season. Conclusion. Based on a recent study on gut-associated lymphoid tissue in A. grypus in two warm and cold seasons revealed that mucosal immunity is more active in the cold season than in the warm season.

Keywords

• gut-associated lymphoid tissue
• GALT
• immunohistoc