HDL decreases thrombocytopenia induced by high-dose VWF injection in ADAMTS13-deficient mice. Mice deficient in ADAMTS13 were injected with saline (n = 3), VWF (n = 4), or VWF plus HDL (n = 3). Blood was drawn from each mouse before and at 3 and 6 hours after the injection. (A) VWF levels in plasma were measured by ELISA. P values for the comparisons of means for VWF vs VWF plus HDL at 3 and 6 hours are <.001 and .05, respectively, from Welch’s t test. (B) Platelets labeled with antibody to CD41 in a Trucount tube were quantified by flow cytometry. Platelet counts at 3 and 6 hours were normalized to the counts at baseline from the same mouse and expressed as percentages of the baseline counts. P values for the comparisons of means for VWF vs VWF plus HDL at 3 and 6 hours are both <.05 from Welch’s t test.