Unique cellular characteristics of the splenic marginal zone of the Barki sheep make it a powerful immunological defense

The marginal zone is a unique structure at the marginal area of the splenic white pulp, acting as a transient region where newly arriving cells, antigens, and blood are filtered. The splenic marginal zone of the Barki sheep surrounds the white pulp and is present between the white and red pulp. It is made up of marginal zone sinuses and diffuse lymphoid tissue aggregation peppered with smooth muscle cells and erythrocytes and supported by reticular cells. Rod-shaped endothelial cells seating on an interrupted basement membrane are lining the marginal zone sinus, which is surrounded by the diffuse lymphoid tissue of the marginal zone, which is formed from different stages of maturation of: lymphocytes, plasma cells, dendritic cells, neutrophils, marginal zone macrophages, erythrocytes, platelets, and reticular cells, all of which are supported by a network of reticular fibers and smooth muscles. Motile lymphocytes with pseudopodia are present in the splenic marginal zone of the Barki sheep. Two forms of smooth muscles are also present: solitary and doubled reciprocal smooth muscles, which give the spleen a powerful ability to filter the blood and provide defense against foreign antigens, making it a unique intermediate type of spleen.