Fig 2: Analysis of C1s levels in plasma samples by EDTA‐gelatin zymography and ELISA: A, Representative pictures of two EDTA‐gelatin zymography gels from the analysis of plasma samples from healthy controls and SLE patients. B, Quantification of the gelatinolytic protein levels after EDTA‐gelatin zymography of 20 healthy control and 22 SLE patient plasma samples. P values were determined by ANOVA Kruskal‐Wallis test, ***P < 0.001. C, The histograms represent the mean concentrations of C1s from 22 plasma samples of SLE patients and 20 healthy individuals, as measured by ELISA. P values were determined by ANOVA Kruskal‐Wallis test, **P < 0.01. D, Correlation analysis of the data from the EDTA‐gelatin zymography in panel B and C1s ELISA from panel C

Fig 3: Corroboration of C1s as the unknown protease: A, similar volumes of the selected fractions from the first anion exchange chromatography analyses were tested by gelatin zymography in the absence (a) or presence (b) of 10 m mol L−1 EDTA, or by Western blot analysis, to identify MMP‐9 (c), MMP‐2 (d), C1r (e), and C1s (f). B, Quantification of the bands from panel A. PL: plasma, WB: Western blot, F: fraction, A.U.: arbitrary units

Fig 4: Study of the presence of C1s in IC: (A and B), 50 μl volumes of plasma samples from healthy controls and SLE patients were incubated with protein‐G‐Sepharose to precipitate the IgG and IgG‐IC. The bound fractions were analyzed by gelatin zymography in the absence (A) or presence (B) of 10 m mol L−1 EDTA. C, Western blot analysis of the same fractions shown in panels A and B for the detection of C1s. D, Quantification of the bands at 90‐80 kDa detected in the zymography from panel B. E, Quantification of the Western blot analysis. P values were determined by ANOVA Kruskal‐Wallis test, *P < 0.05