The contribution of synovial cells to the pathogenesis of rheumatoid arthri
tis (RA) is only partly understood. Monoclonal antibody (mAb) 1D5 is one of
very few mAb ever raised against RA synovial cells in order to study the b
iology of these cells. Studies on the expression pattern and structural fea
tures of the 1D5 Ag suggest that 1D5 recognizes human vascular cell adhesio
n molecule-1 (VCAM-1), which is an intercellular adhesion molecule. Vascula
r cell adhesion molecule-1 may be involved in a number of crucial intercell
ular interactions in RA.