Vascular cell adhesion molecule 1 (VCAM-1), also known as CD106, is a transmembrane glycoprotein belonging to the immunoglobulin gene superfamily. VCAM-1 is expressed by cytokine-activated endothelium, interacts with integrin VLA4 (α4β1) present on the surface of leukocytes, and mediates both adhesion and signal transduction. It is also expressed either constitutively or inducibly in a variety of other cell types, including vascular smooth muscle cells, differentiating skeletal muscle cells, renal and neural epithelial cells, macrophages (Kupffer cells), dendritic cells, and bone marrow stromal cells. Soluble VCAM-1 (sVCAM-1) has been found in addition to membrane-bound VCAM-1. Increased sVCAM-1 has been shown to correlate with disease activity in various entities including rheumatoid arthritis, systemic lupus erythematosus, and lupus nephritis.