Vascular cell adhesion molecule-l (VCAM-l), a member of the immunoglobulin (Ig) supergene family, is expressed on activated, but not resting, endothelium. The principal receptor for VCAM-1, the integrin very late antigen 4 (VLA-4, α 4 β 1 ), is expressed on many lymphocytes including circulating eosinophils, basophils, and monocytes, but not neutrophils. Antibodies to either protein are effective at inhibiting leukocyte infiltration and preventing tissue ...