Endothelial cells play multiple physiological functions and are central to many pathological processes. The liver contains two distinct endothelial cell types: vascular and sinusoidal. Sinusoidal endothelial cells (SEC) are microvascular endothelial cells with a unique phenotype reminiscent of dendritic cells and a unique function as antigen-presenting cells for CD4+ T cells. Thus, SEC represent a new type of organ-resident "non-professional" antigen-presenting cell that appears to be involved in the local control of the immune response and the induction of immune tolerance in the liver. The hepatic microenvironment, i.e. portal venous constituents and soluble mediators from sinusoidal cell populations, tightly control antigen presentation by SEC to avoid immune-mediated damage. SEC express well-characterized surface receptors and differ morphologically and metabolically from large-vessel endothelia. It has reported that SEC are dynamic regulators of porosity that respond rapidly and locally to environmental zonal stimuli during liver regeneration. Due to its strategic position in the liver sinusoid, SEC dysfunction and structural alterations have far-reaching repercussions for the whole liver. HHSEC from AcceGen Research Laboratories are isolated from human liver. HHSEC are cryopreserved immediately after purification and delivered frozen. Each vial contains >5×10^5 cells in 1 ml volume. HHSEC are characterized by immunofluorescent method with antibodies to vWF/Factor VIII and CD31 (P-CAM). HHSEC are negative for HIV-1, HBV, HCV, mycoplasma, bacteria, yeast and fungi. HHSEC are guaranteed to further expand for 15 population doublings in the conditions provided by AcceGen Research Laboratories.