EXPRESSION OF FAS ANTIGEN AND FAS LIGAND IN THE RHEUMATOID SYNOVIAL TISSUE

To understand the role of apoptosis through Fas/Fas ligand (Fas-L) int eraction in the pathogenesis of rheumatoid arthritis (RA), we examined the expression of Fas antigen, Fas-L, and apoptosis in synovial tissu e obtained from eight patients with RA and five patients with osteoart hritis (OA). Immunohistochemical staining demonstrated the significant expression of Fas antigen and Fas-L in RA synovial tissue compared wi th that in OA synovial tissue. Immunohistochemical staining and the DN A nick end labeling (TUNEL) method were combined and revealed that app roximately 10 to 30% of Fas antigen-expressing cells in the RA synoviu m showed DNA fragmentation characteristic for apoptosis. In double-sta ining analysis, Fas-L was expressed on up to 10% of CD45RO-, CD4-, CD8 -, or CD56-positive mononuclear cells in RA synovial tissue. Our resul ts suggest that activated T cells and natural killer cells infiltratin g into the RA synovium may contribute to the induction of apoptosis of RA synovial and mononuclear cells through Fas/Fas-L interaction. (C) 1996 Academic Press, Inc.