Fig. 2.

NET degradation is impaired in a subset of SLE patients. (A) We activated neutrophils isolated from healthy donors to make NETs, incubated them with 10% sera from our cohort for 6 h, and quantified NET degradation. The cohort is described in Materials and Methods and in Table S1. Each circle corresponds to one individual donor. The samples are grouped into healthy donors, SLE patients, and RA patients as indicated. One hundred percent NET degradation was determined using the serum from the healthy donor of the neutrophils. We arbitrarily considered sera that degrade at least 60% of the NETs within 6 h as normal (horizontal line). Sera from all healthy donors (n = 54, black circles) degraded NETs normally; 36.1% of SLE patient sera (n = 61, open circles) and 3.3% of the RA sera (n = 30, gray circles) degraded NETs poorly. ***P < 0.001; Kruskal-Wallis test with Dunn's post hoc comparisons. (B–D) NETs were exposed to representative sera (labeled B, C, or D in A), fixed and immunostained for myeloperoxidase (green) and histones (red). DNA (blue) was stained with Draq5. Representative micrographs show efficiency of NET degradation, with serum from a healthy donor (B), from an SLE patient who degraded NETs (C), and from an SLE patient who did not disassemble NETs (D). (Scale bar in D, 25 μm for B–D.)