5B9 and 1E12 induce thrombocytopenia and thrombosis in vivo. (A) Evolution of platelet count (PC) after injection of 5B9 (1 μg/g body weight; n = 4), 1E12 (0.3 or 1 μg/g; n = 3) or both Abs (n = 3) in transgenic HIT mice (human FcγRIIA, human G6b-B, human PF4 transgenic, mouse PF4 knockout). At days 1, 2, 3 and 4, 1.4 IU/g of UFH was injected in mice treated with 5B9 (n = 3). Data are represented as mean ± SEM. Mann-Whitney U test was performed to compare the different conditions tested. ∗P < .05. (B-E) Sections of lungs with intravascular thrombi from mice injected with 1E12 1 μg/mL + 5B9 1 μg/mL (B-C) or 5B9 1 μg/mL + UFH 0.1 IU/mL (D-E). (F-K) Sections of lungs without thrombi (controls) in mice injected with 5B9 1 μg/mL (F-G), 1E12 1 μg/mL (H-I), or PBS (J-K). Sections were stained using hematoxylin, phloxine, and saffron (HPS) in panels B,D,F,H,J or immunofluorescence in panels C,E,G,I,K. Scale bar, 100 μm (for HPS staining and 150 μm for immunofluorescence).