Changes in circulating hematopoetic cells in the passive immunization murine model of HIT. HIT was induced in hPF4⁺/FcγRIIA⁺ mice by IV injecting 1 mg/kg of KKO. Pre refers to blood levels drawn before KKO infusion for that cell line. (A) Surface-bound KKO was detected by flow cytometry and then normalized to preinfusion level. (B) Same as panel A, but for blood cell counts. Dashed horizontal line indicates preinfusion level for comparison. Basal pre-KKO absolute platelet count was 948 ± 180 × 10³/µL, and absolute monocyte count was 0.92 ± 0.24 × 10³/µL. Mean ± 1 standard deviation is shown. N = 3 (24-48 hours) to 6 (0-4 hour time points). *P < .01, **P < .001, ***P < .0001 compared with baseline pre value using analysis of variance.