Increased Synovial Expression of the Adhesion Molecules CD66a, CD66b, and CD31 in Rheumatoid and Osteoarthritis

Leukocyte-endothelial interaction mediated by adhesion molecules may play a role in the ingress of inflammatory cells into the rheumatoid (RA) synovial tissue (ST). A number of these molecules have been shown to be up-regulated in the inflamed compared to normal ST. We studied the distribution of two members of the CD66 carcinoembryonic antigen adhesion molecule family, as well as that of CD31, an antigen structurally related to CD66, on various cell types in the RA compared to osteoarthritic (OA) and normal ST. Immunoperoxidase histochemistry was carried out using monoclonal antibodies to CD66a, CD66b, and CD31. This study was performed on ST from 10 patients with RA, 10 with OA, and 4 normal individuals. CD66a and CD66b were expressed on RA and OA ST myeloid cells but not on normal ST lining cells and interstitial macrophages, suggesting that these antigens may be specific markers of diseased compared to normal ST macrophages (P < 0.05). CD31 was present on more RA and OA than on normal ST macrophages. Also, CD31 was present on most RA, OA, and normal ST endothelial cells. Our results indicate that the expression of CD66a, CD66b, and CD31, members of the immunoglobulin superfamily of adhesion receptors, is up-regulated on cells of myeloid origin in the inflamed compared to normal ST. These results suggest that the CD66 antigens and CD31 may be involved in the adhesive events in the inflamed synovium.