The role of TWEAK/Fn14 in the pathogenesis of inflammation and systemic autoimmunity.

Interactions between members of the TNF ligand superfamily with their cognate TNF receptors play a crucial role in maintaining immune homeostasis in normal individuals, while dysregulation of certain TNF-ligands and receptors contributes to the pathogenesis of autoimmunity. Identification of novel members of the TNF ligand and receptor families will promote our understanding of the pathogenesis of systemic autoimmune diseases, thus facilitating the development of novel therapeutic approaches. TNF-like weak inducer of apoptosis (TWEAK), a recently identified member of the TNF ligand family, induces PGE2, MMP-1, IL-6, IL-8, RANTES, and IP-10 in fibroblasts and synoviocytes, and upregulates ICAM-1, E-selectin, IL-8, and MCP-1 in endothelial cells. The receptor for TWEAK, Fn14, is expressed in various organs including the kidney; it is intriguing that some of these chemokines induced by TWEAK are crucial in the pathogenesis of lupus nephritis. Furthermore, others have described upregulated TWEAK expression on the surface of T cells in human lupus. In this paper we review the possible roles of TWEAK/TWEAK receptor interactions in the pathogenesis of inflammatory and systemic autoimmune diseases, with particular focus on systemic lupus erythematosus. TWEAK blockade may be helpful therapeutically in restoration of tolerance, but is more likely to modify inflammatory damage in target organs.