IFNG and rheumatoid arthritis: RA is characterized by the destruction of cartilage and bone by inflammatory cytokines, such as tumour necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) (McInnes and Schett, 2011; Lubberts, 2015), and involves the complex interaction of T helper 1 cells (Th1 cells), Th17 cells, Th2 cells, immunoregulatory cells (such as Treg cells) and monocytes/macrophages.