Composition and function of the blood-spleen barrier in Quasipaa spinosa and the evolutionary level of spleen

This study aimed to explore the splenic histology and evolutionary level of Quasipaa spinosa, and also aimed to identify the existence and function of blood–spleen barrier. Histologic technology, transmission electron microscopy, immunohistochemistry, injection of trypan blue, acid phosphatase(ACP) and alkaline phosphatase(AKP) reaction were used in the study. The results showed that spleen without periarterial lymphatic sheaths (PALS) and germinal centres (GC) had two clearly distinguishable areas including the white pulp and the red pulp with fuzzy boundary. In addition to that, there was no evidence for the presence of a marginal zone, and less ellipsoids were located in the boundary region without periellipsoidal lymphatic sheaths (PELS). The white pulp was surrounded by melano-macrophage centres (MMCs) which was formed by numerous melano-macrophages and MMCs were also located in the white pulp occasionally. A few of mast cells existed in the red pulp and close to the vein. The collagen fibers existed in splenic capsule and splenic cord, especially in the wall of arteriole. The result in the detection by Alphα-naphthyl acetate esterase(ANAE) was negative. The dynamic histology of Q. spinosa after injection of trypan blue showed the blue signal was first discovered in free macrophagocyte in the red pulp after one hour post intraperitoneal injection, and then gradually congregated in splenic cord. The blue signal of diffuse distribution in reticular cells in splenic cord was weakened after twenty-four hours post intraperitoneal injection. No trypan blue was detected in the white pulp, ellipsoids and MMCs throughout the whole course of the dynamic study. Meanwhile, the result of dynamic histology post intracardiac injection was similar to that of intraperitoneal injection, except that the positive signal was discovered half an hour earlier. The result of the detection AKP and ACP on the basis of dynamic histology post intraperitoneal injection showed less ACP was detected in normal spleen, but the ACP content in splenic cords and MMCs had a trend of increasing initially and then decreasing afterwards. In contrast, the AKP remained negative in the whole study.