Seasonal Modulation of Splenic Immune Architecture and Proliferative Activity in the Dromedary Camel (Camelus dromedarius): An Ecological Perspective.

Abstract

Seasonal environmental fluctuations in desert ecosystems impose significant physiological and immunological challenges on mammals. This study investigated the impact of seasonal variation on the histological organization, immune cell distribution, and proliferative activity of the spleen in adult male dromedary camels (Camelus dromedarius). Spleen samples were collected during winter and summer and analyzed using histological, semithin, immunohistochemical (CD3, CD20, and Ki-67), and morphometrical approaches. Histological examination revealed that the splenic architecture in both seasons consisted of distinct white and red pulp regions. However, summer samples exhibited increased thickness of the splenic capsule and trabeculae, along with more prominent lymphoid follicles and enhanced lymphocyte density. Semithin analysis confirmed a higher cellular density within the germinal centers during summer. Notably, specialized vascular structures, including throttle arteries and glomus-like bodies, were more frequently observed in the red pulp during summer. Immunohistochemically, CD3-positive T lymphocytes were predominantly localized in the periarteriolar lymphoid sheath, with a significant increase in their proportion during summer. CD20-positive B lymphocytes were extensively distributed within the white pulp in both seasons, with significant increased cellular density during summer. Ki-67 immunoreactivity demonstrated increased proliferative activity during summer, particularly within germinal centers. These findings demonstrate that the camel spleen exhibits marked seasonal plasticity, characterized by coordinated changes in immune cell distribution, proliferative activity, and vascular specialization. Such adaptations likely contribute to maintaining immune competence under the extreme environmental conditions of desert habitats.