Hemostasis at the site of laser-induced injury. Mice subjected to 6.5 Gy total body irradiation had significantly reduced hematocrit (A), platelet count (B), white blood cell (WBC) count (C), and neutrophil count (D) (n = 6, paired t test). (E) Top panels: Representative images of platelet aggregation identified by Dylight 488 anti-GPIbβ antibody (green) and fibrin clot formation detected by Alexa Fluor 647 anti-fibrin antibody (red) in response to a penetrating vascular injury induced by pulse laser in cremaster arterioles of irradiated mice with or without RBC transfusion (bar = 50 μm); bottom panels: time-dependent changes in the formation of platelet and fibrin clots quantified using mean fluorescence intensity (MFI) of antibody-bound fibrin (left) and platelets (right) from 11 independent experiments (6 transfused with RBCs and 5 with cell-free plasma; 2-way ANOVA, P < .001) (bottom). (F) Representative images of platelet and fibrin hemostatic plugs at the site of an identical laser injury to nonirradiated C57BL/6J mice (bar = 50 μm).