HIT IC-mediated thrombosis in vivo. HIT model mice treated with the HIT-like antibody KKO (20 mg/kg body weight, intraperitoneally) received 2 doses of PRT318 (30 mg/kg body weight) orally via gavage or vehicle only (sterile water). Platelets from donor mice were isolated, labeled with Alexa750-labeled antibodies to GPIX, washed, and injected into HIT model mice one hour before challenge with heparin (1400 U/kg, subcutaneously). Three hours after infusion of heparin, mice were killed, flushed systemically with phosphate-buffered saline, and the lungs were extracted and scanned on a Li-COR Odyssey at 780 nm. (A) Representative images for lungs extracted from mice treated with heparin/KKO in the presence or absence of PRT318. (B) The Thrombosis Score reflects the product of the mean thrombus area (square pixels) and the mean number of thrombi (defined by a signal intensity that is 1.5-fold above the background). The Thrombosis Score is significantly different in vehicle only-treated mice (score = 186.9) versus PRT318-treated mice (score = 25.7). Data are mean ± SEM; n = 6 for each treatment group. *P = .03.