Serum IL-33 NET concentration correlated significantly with patient disease activity assessed by the validated SLE Disease Activity Index (SLEDAI) (35) (Figure 2, A and B), and longitudinal reduction in serum IL-33/MPO complexes was noted in patients with good clinical response to belimumab treatment (36) (Supplemental Figure 1A; supplemental material available online with this article; https://doi.org/10.1172/jci.insight.147671DS1). This evidence concerns the gene MPO and systemic lupus erythematosus.