Characterization of platelet-specific PDI–deficient mice. (A) Polymerase chain reaction (PCR) analysis of WT and PDI CKO mice with primers for floxed PDI (422 bp) and PF4-Cre (450 bp). (B) Lysates of neutrophils, endothelial cells, and platelets isolated from WT and PDI CKO mice were immunoblotted with indicated antibodies. Band density of PDI, ERp57, ERp72, and GRP78 in WT platelets (gray bars) is shown as 100%. White bars, PDI-null platelets. Data represent mean ± SD (n = 3-6 mice per group). **P < .01; ***P < .001 vs WT platelets after Student t test. (C) Flow cytometric analysis shows the surface expression of ERp57 and ERp72 on resting (dotted line) and thrombin-activated (black line) WT and PDI-null platelets. The gray histogram represents the fluorescence intensity of control IgG on thrombin-activated platelets. The geometric mean fluorescence intensity of antibodies was normalized to that of control IgG, and data are shown as a fold increase (mean ± SD, n = 3).