Immunological Adhesion and Homing Molecules

The immunosurveillance function of leukocytes requires a strictly controlled trafficking between lymphoid and nonlymphoid tissues. Thus, white blood cells are continuously scanning the body for sign of infection or damage with lineage‐specific pathways. Triggered by chemokines and other danger signals, those movements require selective interactions mediated by adhesion and homing molecules expressed by immune and endothelial cells. Typically, the transendothelial migration is initiated by specific interactions between selectins and glycosylated proteins, which allow the initial tethering and rolling of leukocytes on endothelial cells. In the presence of chemokines, rolling is followed by firm arrest mediated by active integrins binding to immunoglobulin superfamily ligands and culminates with extravasation. The expression pattern and structural features of those adhesion molecules dictated the cell‐specific homing governing the immune response.