IFNG and rheumatoid arthritis: Perturbed upregulation of IFN-γ can lead to autoimmune diseases, such as rheumatoid arthritis, lupus nephritis, and systemic lupus erythematosus (SLE), in which elevated Th1 versus Th2 cell populations increase IFN-γ levels and the activation and number of destructive proinflammatory macrophages15–18.