Flow cytometric analysis of circulating platelets after induction of thrombocytopenia. Mice were injected with 2.0 µg of polyclonal anti-GPIbα antibody, resulting in a reduction of platelet counts to ∼30% of control after 12 hours (time point of analysis). (A) Expression levels of glycoproteins in platelets of control (shaded area) and depleted animals (gray line) are depicted. (B) A new population of platelets can be identified in the samples of platelet depleted mice (left). If this population is excluded from analysis [based on its forward scatter (FSC)/side scatter (SSC) characteristics], no differences in glycoprotein expression patterns between platelets from control and depleted animals were observed as exemplified here for GPIb (right). Histograms are representative for 8 animals from 2 independent experiments. (C) Flow cytometric analysis of (left) integrin αIIbβ3 activation and (right) degranulation-dependent P-selectin exposure in response to ADP (10 µM), thrombin (Thr; 0.01 U/mL), and convulxin (CVX; 1 µg/mL). Results are means ± standard deviation of 4-5 mice per group.