To isolate disease-associated autoantibodies, we generated 199, 74, and 150 mAb clones from blood CD19low CD138+ plasmablasts (PBs) of untreated acute SLE patients, patients in remission, and healthy volunteers, respectively (Supplementary Fig. 1 and Supplementary Table 1), and tested for their reactivity against representative SLE self-antigens, dsDNA and cardiolipin (CL) in ELISA. Here, SDC1 is linked to systemic lupus erythematosus.