CD106, also known as INCAM-110, is a 110 kDa vascular adhesion cell adhesion molecule-1 (VCAM-1) that is member of the immunoglobulin superfamily. CD106 is expressed predominantly on cytokine-activated vascular endothelium but has also been identified on interfollicular dendritic cells, some macrophages, and bone marrow stromal cells. Endothelial CD106 binds the integrins ?4?1 (CD49d/CD29, VLA-4) and ?4?7 and contributes to extravasation of lymphocytes, monocytes, basophils, and eosinophils (but not neutrophils) from blood vessels, particularly at sites of inflammation. Unlike the ?2 integrins, the CD106-VLA-4 interaction can mediate both the initial tethering and rolling of lymphocytes on endothelium as well as their subsequent arrest and firm adhesion. CD106 expressed on non-vascular tissues has been implicated in the interaction of hematopoietic progenitors with bone marrow stromal cells, B cell binding to follicular dendritic cells, costimulation of T cells, and embryonic development. The monoclonal antibody 1.G11B1 inhibits in vitro binding of lymphocytes and monocytes to VCAM-1 on stimulated endothelium.