Simultaneous flow cytometric analysis of RBCs and platelets in the washed platelet-rich plasma of p45 NF-E2^−/− mice, showing substantial contamination of platelet-sized cells by RBC fragments. (A) Left panel: Forward (FSC-H) and side (SSC-H) scatter characteristics of the platelet population in wild-type mice. In the analysis of wild-type mice (center panel), only platelets (CD41-positive cells) were observed using the scatter characteristics shown in (A). In samples from p45 NF-E2 knockout mice (right panel), a subtantial population of RBC fragments (TER-119–positive) was present, comprising 56% of total events in this analysis of platelet-sized particles. Results were identical in 2 independent experiments. (B) Representative blood smears from adult p45 NF-E2 knockout mice, showing the presence of small RBC fragments (arrows) and absence of blood platelets.