TNF and rheumatoid arthritis: Several of the pro-inflammatory cytokines (e.g., TNF-α, IL-1ß) and other molecules (e.g., Fas, VEGF) implicated in the progression of RA activate the extrinsic apoptosis pathway involving the coupling of a protein ligand to a cognate receptor, whereas the intrinsic apoptosis cascade is initiated when cytochrome c is released from mitochondria.