The role of adhesion molecules in synovial pannus formation in rheumatoid arthritis

To elucidate the mechanism of cell binding to cartilage, using an immunoperoxidase technique with monoclonal antibodies against adhesion molecules, the pattern of distribution of these molecules at the rheumatoid pannus-cartilage junction has been investigated. Treatment with purified anti-human-monoclonal antibody CD54 anti-(ICAM-1) resulted in membrane staining of most of the large cells infiltrating the synovial tissue and bordering the pannus cartilage junction. When the specimen was treated with purified anti-human-monoclonal antibody CDw49d anti-(VLA-4), purified anti-human-monoclonal antibody CDw49e anti-(VLA-5), most of the cells in the cartilage pannus junction stained, but there were few staining cells against purified anti-human-monoclonal antibody CD11a anti-(LFA-1). There were some anti-ICAM-1 and anti-VLA-5 staining of the chondrocytes at or close to the junction. Human umbilical vein ECBBA1 (ELAM-1) staining was only observed on the endothelial cells of postcapillary venules in the synovial tissue. These results show that the specific adhesion molecules tested may play a role in rheumatoid pannus formation and that the increased expression of VLA-4, VLA-5, and ICAM-1 at the cartilage pannus junction may represent interaction with matrix protein. The VLA interaction appear to be involved in pannus attachment, whereas LFA-1 and ICAM-1 are involved in cell-cell interaction and may upregulate molecules such as VLA that are involved in attachment.