The genetic IFN type I signature is present in about 50%–75% of adult patients with SLE.15 We here show that IFNα protein was detectable in intervillous blood from 60% of the SLE pregnancies and that the IFN-responsive gene MX1 was upregulated in decidual stromal cells from five out of six women with SLE. This evidence concerns the gene MX1 and systemic lupus erythematosus.