Journal: Frontiers in Immunology

Article Title: Molecular determinants of STEC-HUS: from complement activation to microvascular thrombosis

doi: 10.3389/fimmu.2026.1749811

Figure Lengend Snippet: Prothrombotic effects of STEC-HUS serum are dependent on WPB exocytosis from endothelial cells. P-selectin (A) and vWF (B) expression on unstimulated HMEC-1 exposed to serum from patients with acute STEC-HUS (n = 5 for P-selectin experiments; n = 6 for vWF experiments), in the presence or in the absence of different complement inhibitors (sCR1, 150 µg/mL; factor B inhibitor, iptacopan,10 µM; eculizumab 100 µg/mL) or to a pool of control sera (normal human serum, NHS), run in parallel. Results are shown as pixel 2 /high-power field (HPF) of stained surface area. Data are mean ± SD. Circles represent single patients’ data. The addition of either sCR1, or iptacopan or eculizumab to patient’s serum significantly decrease both P-selectin and vWF expression induced by patient’s serum alone. *P < 0.05 vs STEC-HUS serum alone (ANOVA, followed by Tukey’s multiple comparisons test for data of P-selectin expression and by Holm-Šídák’s multiple comparisons test for data of vWF expression). (C) Endothelial surface area covered by thrombi on ADP-activated HMEC-1 exposed to serum from STEC-HUS patients collected during the acute phase of the disease and then perfused with whole blood. Before the experiments, HMEC-1 were left for 16 hours with medium added or not with the RalA inhibitor BQU57 (10 µM). Data are expressed as mean ± SD of percentages of serum-induced thrombus formation in respect to a pool of control sera (normal human serum, NHS), run in parallel in each experiment and set as 100% (n = 3 independent experiments). Circles indicate single patients’ data. Horizontal dashed lines indicate upper and lower limits of the normal range . *P < 0.05 (paired Student’s t test). (D) Representative confocal microscopy images (original magnification X200) of experiments of thrombus formation (green staining) relative to Figure 6C . Scale bar: 100 µm.

Article Snippet: Cells were washed again and treated with the following specific antibodies: FITC-conjugated rabbit anti-human C3c-complement (Dako, that recognizes C3c, part of C3 and C3b, 1:300 final dilution in Dapi 1 μg/mL); or rabbit anti-human complement C5b-9 complex (Calbiochem, 1:200 final dilution in PBS1X) followed by FITC-conjugated secondary antibody (Jackson ImmunoResearch Laboratories, 1:50 final dilution in 1 μg/mL Dapi); or goat anti-human C4 (Abcam, 1:100 final dilution in PBS1X) followed by Cy3-conjugated secondary antibody (Jackson ImmunoResearch Laboratories, 1:200 final dilution in Dapi 1 μg/mL); or FITC-conjugated anti-human IgG (Sigma Aldrich, 1:32 final dilution in 1 μg/mL Dapi); or mouse anti-human P-selectin (R&D System, 20 μg/mL final concentration in PBS1X), followed by Cy3-conjugated secondary antibody (Jackson ImmunoResearch Laboratories, 1:60 final dilution in 1 μg/mL Dapi); or rabbit anti-human vWF (Dako, 10 μg/mL final concentration in PBS1X), followed by Cy3-conjugated secondary antibody (Jackson ImmunoResearch Laboratories, 1:50 final dilution in 1 μg/mL Dapi).

Techniques: Expressing, Control, Staining, Confocal Microscopy