Apolipoproteins are plasma lipoproteins that function as transporters of lipids and cholesterol in the circulatory system. Apolipoprotein-D (Apo-D) is mainly associated with high density lipoproteins in human plasma. It is expressed in numerous tissues having high levels of expression in spleen, testes and brain. Apo-D is a multi-ligand, multi-functional transporter and transports a ligand from 1 cell to another within an organ, scavenge a ligand within an organ for transport to the blood or could transport a ligand from the circulation to specific cells within a tissue.
