Fig. 3

NETs from SLE patients are enriched in ISG15 and H2B is the main substrate. ISG15 and H2B expression was assessed in spontaneous and LPS induced NETs from SLE patients (n = 6) and healthy controls (n = 3) by indirect immunofluorescence (40X) and confocal microscopy. Spontaneous NETs from a representative SLE patient shows the presence of extracellular ISG15 in the NET (a). In contrast to the SLE sample, a representative healthy control image shows the absence of ISG15 in the NET (b). Blue (DNA), red (ISG15) and green (H2B). Cumulative data from SLE patients and healthy controls (n = 6 subjects per group) show increased expression of ISG15 in the SLE samples (c). In SLE samples, ISG15 and H2B colocalized inside NETs with a high Pearson (R = 0.81) and Costes p value (1.0) in a representative SLE patient (d) and boxes represent pooled data (n = 6 subjects per group) that show increased colocalization of SLE samples vs healthy controls (e). H2B with ISG15 had the higher colocalization R value compared to other NET proteins such as LL37 or HMGB1 (Additional file 1: Figures S5 and S6). * p < 0.05