Figure 1: An Apoptotic/Survival Cascade in Synovial Fibroblasts: Regulation via Fas (CD95), TNF-α and Growth Factor Receptors. Apoptosis or survival of synovial fibroblasts can be induced by several types of ligand-receptor interactions. These interactions may involve Fas, cytokine or growth factor receptor activation. P, site for MAPK-mediated phosphorylation.