IFNG and systemic lupus erythematosus: Similarly, levels of IFN-α but not levels of IFN-λ1 protein correlated with poor response to immunosuppressive therapy in patients with SLE [80], while a reduction in serum IFN-γ protein levels was associated with response to ustekinumab, an anti-interleukin-12/-23 monoclonal antibody (mAb), in a phase two SLE trial [97].