Dendritic cells (DC) are antigen-presenting immune system cells that are present on peripheral mucosal tissues and migrate to lymphoid tissues. DC-SIGN (DC-specific ICAM-3 grabbing nonintegrin) is a type II membrane protein that is exclusively expressed by DC. DC-SIGN, also designated CD209, binds to ICAM-3 to mediate the initial interaction between DC and resting T cells through the immunological synapse. The DC that are present in the initial sites of HIV-1 infection capture HIV-1 through DC-SIGN, which then facilitates the migration of DC to areas of T cell-rich secondary lymphoid organs, where it promotes efficient trans HIV-1 infection of these T cells. DC-SIGNR (DC-SIGNrelated molecule), also designated CD209L and L-SIGN (liver/lymph nodespecific ICAM-3 grabbing nonintegrin), is a type II integral membrane protein that is 77% identical to DC-SIGN. It is expressed on sinusoidal endothelial cells and binds the E2 glycoproteins of the hepatitis C virus.
