Architecture of the Blood‐Spleen Barrier in the Soft‐Shelled Turtle, Pelodiseus Sinensis

Abstract

We investigated the structure of the soft-shelled turtle, Pelodiseus sinensi, spleen and demonstrated that there were several microanatomical peculiarities by light and transmission electron microscopy. In the spleen, the white pulp of the spleen was composed of two compartments, the periarteriolar lymphatic sheath (PALS) and periellipsoidal lymphatic sheath (PELS). No lymph nodules and marginal zones were found. The spleen-blood barrier stood in the PELS and the ellipsoid. The high endothelial lining of penicilliform capillary contained small channels. These channels allowed circulating substances or lymphocytes to enter the ellipsoid. The distal portion of the penicilliform capillaries directly opened to pulp cords. The ellipsoid-associated cell (EAC) was located at the surface of the ellipsoid. Reticular fibers were mainly distributed in ellipsoid and the outer PELS. Both reticular cells and macrophages were distributed in the outer layers of PELS. S-100 protein positive dendritic cells were mainly distributed in out cells layer of the PELS and all over the PALS. Forty minutes after injection, carbon particles of Indian ink were mainly observed in the ellipsoid. Few carbon particles were observed in the outer PELS and fewer carbon particles in the red pulp. These findings suggested that a blood-spleen barrier indeed existed in the soft-turtle, P. sinensi, and it was a complex composed of an ellipsoid (including supporting cells, EAC, and reticular fibers) and the outer compartments of PELS (including dendritic cells, reticular fibers and cells, macrophages).

The spleen morphophysiology of fruit bats

“…Moles, pigs, cats and dogs have numerous and wide ellipsoids, while horses, cows and sheep have medium ellipsoids sizes (Bacha & Bacha, ; Blue & Weiss, ; Press & Landsverk, ; Snook, ). Ellipsoids have a strategic function as filtration of bloodborne pathogen as well as marginal zones (Blue & Weiss, ; Boes & Durham, ; Steiniger, ) and take a role as a major site of blood pathogen filtration in soft‐shelled turtles and chickens that do not possess a marginal zones (Bao, Li, Wang, Qin, & Xu, ; Zhang et al, ). A large number of ellipsoids in the fruit bats indicate that the central arteries branch out many capillaries.…”

Evolution of lymphoid tissues

“…The structure of the spleen in amphibia is similar to that of fishes, with the exception that reticular cells are present in the follicle areas [67]. The spleens of reptiles [68] exhibit a somewhat more elaborate microanatomical structure, but still lack the canonical germinal centers (GCs) that were first recognizable in the spleen of birds [69]. In the mammalian spleen, a further functional advance seems to be the emergence of a specialized antigen-trapping device, the marginal zone, populated by a certain type of macrophage [70].…”

Morphological characterization of postembryonic development of blood–spleen barrier in duck

“…They reported that the BSB is composed of splenic sinus endothelial cells, vascular basement membrane, reticular cells, and macrophages. The BSB is a kind of immune barrier, functioning as a mechanical and biological barrier, and presenting antigens to maintain a stable spleen microenvironment ( Bao et al., 2009 ).…”