TNFSF15 and rheumatoid arthritis: TNF-like ligand 1A (TL1A) is a newly described member of the TNF superfamily that has been shown to be involved in promoting a range of autoimmune diseases including IBD, rheumatoid arthritis (RA), and asthma through the generation and activation of the type-1 T helper cell (TH1) and type-17 T helper cell (TH17; Bamias et al., 2003, 2006; Bull et al., 2008; Fang et al., 2008).