Stx1B and Stx2B induce endothelial VWF secretion and platelet adhesion in a dose-dependent and -specific manner. VWF deposition on HUVECs in response to Stx1B (■) or Stx2B (□) was tested under static conditions (A) and under laminar flow (B). VWF secretion was inhibited by preincubating Stx2B with anti-Stx2B monoclonal antibody 5H8 (10 μg/mL; C), or by preincubating Stx1B with polyclonal anti-Stx1B antiserum (2 or 4 μL/mL; D); anti-Stx2B did not inhibit Stx1B, and anti-Stx1B did not inhibit Stx2B (E). (F) Stx1B and Stx2B (ng/mL) induced platelet adhesion to HGMECs. Experiments were repeated at least 2 (C-F) or 3 times (A-B) with similar results. Values are shown as mean ± SE. Indicated comparisons of Stx1B and Stx2B are significant at P < .05 (*) or P < .01 (**) by Student t test.