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: Characterization and optimization of C1s detection by zymography: A, Fractions 59 and 67 (30 μl) from the first anion exchange were analyzed by gelatin zymography in the presence or absence of 10 m mol L−1 of EDTA and/or Ca2+. B, Example of quantification of the gelatinolytic bands from panel A. C, Zymography analysis of selected fractions from the anion exchange in the absence (CONTROL) or presence of 10 m mol L−1 EDTA (+EDTA). D, The levels of C1s were measured by ELISA in the same fractions, as analyzed in panel C. A.U.: arbitrary units