TNF and rheumatoid arthritis: Initially discovered as a serum factor which induced cell death in tumour cells1 and thought at that time to be a promising target as a cancer treatment, TNF was later realised to be a potential target for the treatment of inflammatory diseases, such as rheumatoid arthritis (RA)3, Crohn’s disease (CD)4, ankylosing spondylitis (AS)5, and psoriasis6.