TNF and psoriatic arthritis: Biological therapies such as anti-tumor necrosis factor (TNF) and anti-interleukin antibodies are widely used for a range of immune-mediated inflammatory diseases (IMIDs), including rheumatoid arthritis (RA) (Smolen et al., 2016), psoriasis (PsO), and psoriatic arthritis (Boehncke and Schon, 2015), Crohn’s disease (CD) (Baumgart and Sandborn, 2012) and ulcerative colitis (UC) (Ordás et al., 2012; Fiorino et al., 2014).