Glucocorticoids are widely used to treat patients with autoimmune diseases such as systemic lupus erythematosus (SLE), but many treatment regimens cannot maintain disease control in SLE patients. Here it is shown that the stimulation of plasmacytoid dendritic cells through toll-like receptors TLR7 and TLR9 can account for the reduced activity of glucocorticoids to inhibit the type I interferon pathway in SLE patients. Thus inhibitors of TLR7 and TLR9 signalling might prove to be effective corticosteroid-sparing drugs.