Abstract
The splenic sinuses form a specially differentiated unique vascular system. In this study, human spleens were examined electron microscopically and immunohistochemically. The endothelial cells were elongated and lay parallel to the long axis of the sinus. Furthermore, the cells were laterally bound to each other by slender side processes. Interendothelial slits were formed between these processes. Reticular fibers bundled the outside of the sinus similar to hoops embracing staves of a barrel. On immunohistochemistry, sinus endothelial cells were positive for CD4, CD8 and monocyte/macrophage marker in addition to vimentin, factor VIII and UEA-1. Human spleen had a open circulation and blood flowed from the penicillar artery into the splenic cord. The interendothelial slits of the sinus were the major passage way of blood from the splenic cord into the sinus and played an important role in filtering aged or damaged cells from circulation.
Splenic sinuses in idiopathic portal hypertension (IPH) were further studied. In IPH, proliferation of sinus endothelium was activated as compared that in liver cirrhosis. HLA-DR expression was also increased in the sinus endothelium. Scanning electron microscopy disclosed that sinus endothelium were irregular in shape and the interendothelial slits were enlarged.
