Figure 5.

ADAMTS13 is involved in immune-mediated thrombotic thrombocytopenic purpura IgG-induced Weibel-Palade bodies degranulation. (A) Von Willebrand Factor (VWF) quantification by enzyme-linked immunosorbant assay in the supernatants of cells treated with immune-mediated thrombotic thrombocytopenic purpura (iTTP) serum (n=5) or hereditary TTP serum samples (hTTP, n=5, *P<0.05). (B) Fluorescence intensity (AU) of Ca²⁺ flux induction in permeabilized human microvascular endothelial cells from derm (HMVEC-d) after a 20-second incubation with serum from iTTP patients (n=5) or from hTTP patients (n=5, **P<0.01). (C) ADAMTS-13 mRNA relative quantification in HMVEC-d cultured in the presence of control small interfering RNA (siRNA) (Ct si) or siRNA targeting ADAMTS13 (ADAMTS13 Si) (n=6, *P<0.05). (D) Fluorescence intensity (AU) of Ca²⁺ flux induction in HMVEC-d transfected with control or anti-ADAMTS13 siRNA, then stimulated for 20 seconds with IgG from iTTP plasma samples (n=15, **P<0.01). (E) VWF expression detected by fluorescence microscopy in HMVEC-d incubated with IgG from control patient samples (a) TTP73-1 monoclonal antibody (mAb) (B) or ELH2-1 mAb (C) (original magnification X40, scale bar=30 mm). (F) VWF or (G) endothelin-1 concentrations in supernatants of HMVEC-d incubated with IgG from control patient samples (Control) (n=3), TTP73-1 or ELH2-1 mAb (n=5, *P<0.05). (H) Fluorescence intensity (AU) of Ca²⁺ flux measured at 20 seconds in HMVEC-d stimulated in a similar fashion as in (G) (n=3, ns: not significant).