Neighborhood politics: the immunoregulatory function of organ-resident liver endothelial cells

The liver is known for its ability to induce antigen (Ag)-specific immune t olerance. Among the different cell populations involved in the induction of hepatic tolerance, the liver sinusoidal endothelial cells (LSECs) are part icularly important because they are highly efficient at presenting soluble Ags to CD4(+) and CD8(+) T cells. The crosspresentation of soluble Ags to C D8(+) T cells was believed previously to be restricted to professional Ag-p resenting cells (APCs) such as dendritic cells (DCs). However, in contrast to DCs, crosspresentation by LSECs can induce Ag-specific immune tolerance. It is proposed that these organ-resident APCs act as sessile hepatic APCs that control the immune responses to soluble blood-borne Ags, in concert wi th APCs in lymphatic tissue.