IFNG and rheumatoid arthritis: There is a possibility that SOCS1 induction may be associated with the ability of CD4+ T cells to produce IFN-γ, because CD4+ T cells from active RA could produce high levels of IFN-γ in the presence of IL-10, and because IFN-γ has been known as a potent inducer of SOCS1 [32].