Abstract
Simple SummaryThe spleen is a separate organ of the teleost, playing an essential role in immune reactions. The morphology of the spleen is different from the fish species. Little knowledge about the spleen structure and the blood splenic barrier (BSB) in Nile tilapia has been reported. The present study showed that the spleen of Nile tilapia could be portioned into three subregions, and the BSB lay in the middle layer, composed of the cuboidal-shaped endotheliocytes and the surrounding reticular fibers of the ellipsoid capillaries. Our results enriched the research of immune tissues and system in tilapia and provided reference for the study of spleen in other fish species.The spleen is a separate organ of the teleost, playing an essential role in immune reactions. The morphology of the spleen is different from the fish species. Little knowledge about the spleen structure and the blood splenic barrier (BSB) in Nile tilapia has been reported. To address this issue, we studied the histology of the spleen and the BSB in healthy Nile tilapia. The morphology of the spleen was observed, then H&E staining, modified Jame’s staining, and ultrastructural techniques were performed to portion the spleen into three subregions and analyze the location of components and fibers. Thereafter, vital staining of Nile tilapia with Trypan blue was conducted to elucidate the composition and function of BSB. Histologically, the spleen could be divided into three subregions (inner, middle, and outer). The venules, clumps of lymphocytes, and vessels were separately characterized features of the outer, middle, and inner layers. Post injection, Trypan blue was intercepted in the endotheliocytes of ellipsoids in the middle layer (i.p.) or was deposited to the reticular fibers surrounding the ellipsoids (i.v.). Additionally, the amount of Trypan blue was shown to be positively correlated to that of the Acid phosphatase expressed. In conclusion, the spleen could be portioned into three subregions, and the BSB lay in the middle layer, composed of the cuboidal-shaped endotheliocytes and the surrounding reticular fibers of the ellipsoid capillaries. The present study enriched the research of immune tissues and system in tilapia and provided reference for the study of spleen in other fish species.
Highlights
It is necessary to improve the knowledge on fish immune organs since they are closely related to the immune responses
The spleen lay in the peritoneal cavity, covered by the liver post-dissected from the left side of the body and was adjacent to the anterior gut wall and the stomach observed from the right side of Nile tilapia (Figure 1A)
We found that the blood splenic barrier (BSB) existed in the middle layer, composed of the endotheliocytes
Summary
It is necessary to improve the knowledge on fish immune organs since they are closely related to the immune responses. Techniques for investigating immune responses have been widely used, such as RT-qPCR for the expression of immune genes, immunohistochemistry (IHC) or ELISA for immune proteins, and flow cytometric method for immune cells [1,2,3]. The histological technique is a gold standard widely used in human diagnosis and prognosis [4]. Its application in teleost was limited due to the differences of morphology and histology among species [5]. The spleen, as one of the most important immune organs of teleost, plays essential roles in filtering and removing foreign agents or effete blood cells and secreting antibodies
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
