Figure 1 : Presence of blocking autoantibodies to IFNα in SLE subjects.

(A) Bar graph depicts arbitrary units (AU) of anti-IFNα autoantibodies measured by ELISA in 10 SLE subjects who developed RT-PCR- confirmed COVID-19 between April 1^st and October 1^st, 2020. Horizontal dotted line shows 2 standard deviations above mean of 119 healthy controls (55 AU), individual subjects are separated by vertical dotted line, missing plasma samples are represented by X. Plasma samples from Patient 3 and 9 (boxed) had blocking antibodies. (B) Representative example of detection of blocking anti-IFNα autoantibodies. Healthy control PBMCs were incubated with 10% plasma from healthy controls or from autoantibody-positive or negative SLE subjects with COVID-19, and then left unstimulated or stimulated with recombinant human IFNα. IFN-induced phosphorylation of STAT1 was measured by flow cytometry.