Platelet binding and aggregation on TNF-α–prestimulated HUVECs.

(A) Unstimulated (ie, not incubated with Stx) HUVECs incubated with monoclonal anti-Stx1 and goat-antimouse immunoglobulin FITC. No FITC labeling observed. (B) HUVECs incubated for 2 hours with 100 pg/mL Stx1. Stx1-FITC labeling noted in cells. (C) HUVECs incubated with platelets without Stx1. Scattered platelets noted. (D) HUVECs incubated with 100 pg/mL Stx1 and platelets. Platelet aggregates containing Stx1-FITC and platelet binding to HUVECs noted (panels C and D show combined staining FITC-Stx and anti CD41-PE). (E) HUVECs incubated with 1 ng/mL Stx1 and platelets showing platelet binding to the circumference of HUVEC (see arrow, FITC-Stx and anti CD41-PE). (F) HUVECs incubated with 100 pg/mL Stx1 and platelets. Arrow shows platelet aggregate containing Stx1-FITC binding to HUVEC. (G, H) HUVECs incubated with 100 pg/mL (G) or 10 pg/mL (H) Stx1B and platelets showing uptake of Stx1B in both cell types, aggregation of platelets, and binding to HUVECs (FITC-Stx and anti-CD41–PE). Magnifications: A-E and G-H, × 400; F, × 1300.