The spleen morphophysiology of fruit bats

Abstract

Spleen is one of the important lymphoid organs with wide variations of morphological and physiological functions according to species. Morphology and function of the spleen in bats, which are hosts to several viral strains without exhibiting clinical symptoms, remain to be fully elucidated. This study aims to examine the spleen morphology of fruit bats associated with their physiological functions. Spleen histological observations were performed in three fruit bats species: Cynopterus titthaecheilus (n = 9), Rousettus leschenaultii (n = 3) and Pteropus vampyrus (n = 3). The spleens of these fruit bats were surrounded by a thin capsule. Red pulp consisted of splenic cord and wide vascular space filled with blood. Ellipsoids in all three studied species were found numerously and adjacent to one another forming macrophages aggregates. White pulp consisted of periarteriolar lymphoid sheaths (PALS), lymphoid follicles and marginal zone. The lymphoid follicle contained a germinal centre and a tingible body macrophage that might reflect an active immune system. The marginal zone was prominent and well developed. This study reports some differences in spleen structure of fruit bats compared to other bat species previously reported and discusses possible physiological implications of the spleen based on its morphology. K E Y W O R D S flying foxes, histology, immunology, morphology, physiology, viral reservoir

Extracellular matrix composition of different spleen compartments of fruit bats

“…The presence of PELS‐like structure is thought to be an additional mechanical barrier structure of fruit bats' spleen that is not shared by other species of mammals in general. These findings support the primary function of fruit bats spleen as blood pathogen filtration organs (Hanadhita et al, ). A further study to identify the phenotype of the associate cells around reticular ring would be needed to ascertain the PELS structure and its function in fruit bats.…”

“…Visualization of the reticular meshwork can better demonstrate some splenic compartments. Hanadhita et al () described the presence of vascular space in the spleen of the fruit bats and have not yet been able to ascertain whether the structure is sinuses or venules. In this study, vascular space was identified as being limited by reticular fibres.…”

“…In this study, we have used the spleen specimen of C. titthaecheilus ( n = 9) and R. leschenaultii ( n = 3) fixed with 4% Bouin and embedded in paraffin from our previous studies (Hanadhita et al, ). The paraffin‐embedded tissue was cut to 5 μm thickness.…”

“…In fruit bats, reticular fibre networks build the stromal structure of white and red pulp of the spleen. The white pulp structures of fruit bats spleen consist of follicles, periarteriolar lymphoid sheaths (PALS), marginal zones (MZ) and marginal sinuses (MS), while the red pulp is composed by splenic cord meshwork which also contains ellipsoid and vascular space structures (Hanadhita et al, ). Based on morphological studies, the spleen of fruit bats is thought to be dominated by filtration and defence functions (Hanadhita et al, ), which function is primarily determined by the interaction of the cells and ECM in a particular area of the spleen.…”

“…The white pulp structures of fruit bats spleen consist of follicles, periarteriolar lymphoid sheaths (PALS), marginal zones (MZ) and marginal sinuses (MS), while the red pulp is composed by splenic cord meshwork which also contains ellipsoid and vascular space structures (Hanadhita et al, ). Based on morphological studies, the spleen of fruit bats is thought to be dominated by filtration and defence functions (Hanadhita et al, ), which function is primarily determined by the interaction of the cells and ECM in a particular area of the spleen. This study was conducted to identify the distribution of reticular fibre and other constituents ECM in various spleen compartments of fruit bats, namely Indonesian short‐nosed fruit bats ( Cynopterus titthaecheilus ) and Leschenault's rousette ( Rousettus leschenaultii ).…”