The vascular lining cells in the human spleens include littoral cells (LCs) and other splenic vascular endothelial cells (SVECs). LCs that comprise about 30 percent of the splenic red pulp are specialzed endothelial cells distinct from SVECs. They line the splenic sinusoids and function as the filters and scavengers for senescent or altered red blood cells. Patients with advanced forms of myelofibrosis (MF) often develope extramedullary hematopoiesis in the spleen.Vascular lining cells within MF spleens are thought to serve as a supportive microenvironment for MF hematopoietic cells. In this study we isolated MF and normal LCs and SVECs from human spleens using immunostaining and flow cytometric sorting and used microarrays to analyze the underling mechanism of LCs' unique functions that distinguish them from SVECs, and the properties of MF LCs and SVECs and their contributions to the microenvironment of MF spleens.