New Insights into the Splenic Stroma of the Barki Sheep: A Histological, Immunohistochemical, Ultrastructural and Morphometrical Study

Abstract

Introduction: Spleen is the largest secondary lymphatic organ in the body designed to respond immunologically to antigens circulating in the blood. Aim: describe the histoarchitectural features and morphometrical characters of the stroma of the Barki sheep’s spleen. Materials and Methods: the splenic stroma of 30 clinically healthy Barki sheep was studied using different histological, immunohistochemical, ultrastructural, and morphometrical techniques. Results: A prominent layer of smooth muscles with few sporadic collagen fibers form the capsule which was 676.29 μm and has a subcapsular sinus. Meanwhile, the trabeculae which were composed mainly of smooth muscle cells originate from the capsule into the splenic parenchyma branch into primary (517.095 μm thick), secondary (470.609 μm thick), and tertiary trabeculae (382.27 μm thick). The subcapsular blood sinuses and the peritrabecular blood sinuses all are connected and are engorged with blood cells mainly CD3+ T lymphocytes. Conclusion: the high amount of smooth muscles and very thick stroma is unique to Barki sheep’s spleen denoting an efficient storage function beside the defensive function. CD3 T lymphocytes in subcapsular and peritrabecular sinuses are to form a link between primed T lymphocytes and the underlying stromal elements, creating microenvironments suitable for effector responses.