Characteristics of platelet-like particles in NF-E2–deficient mice. (A) Forward scatter (FSC) plot of control (p45 NF-E2^+/−, left) and p45 NF-E2^−/−(right) platelets, as defined by fluorescent staining with 2D5 (shown as 2D5-FITC on the ordinate). Control samples showed the same forward scatter characteristics (FSC, an estimate of cell size) as wild-type mouse platelets, whereas p45 NF-E2^−/− samples included heterogeneous subpopulations of particles exhibiting similar scatter characteristics to platelets, as well as particles that failed to bind 2D5. (B and C) Representative flow cytometry histograms of platelets (2D5⁺ cells) reacting with the anti–P-selectin antibody RB40. The majority of 2D5+ particles from NF-E2–null mice do not express P-selectin after stimulation with bovine thrombin (B) or phorbol myristate acetate (PMA; C). The shaded curves represent staining of unstimulated cells (background) while the clear curves show P-selectin expression after stimulation with thrombin (B) or PMA (C). All events were gated on 2D5 positivity, the data are representative of 7 (B) and 4 (C) similar experiments, respectively, and the numbers are presented in greater detail in Table 1.