Fig. 2. Scatter plots and bar graph with arithmetic means ± SEM showing annexin-PE binding to O RBCs and its dependence on serum complement activity. O RBCs incubated with serum (stored at 4° C for 48 h) from a patient with cold AIHA did not show increased PS exposure (A). Whereas supplementary addition of fresh AB serum as a source of complement induced significantly (p<0.001) PS exposure (B, G), no effect could be seen after addition of heat-inactivated (i.a.) AB serum (C, G). Similarly, i.a. serum from a patient with cold AIHA did induce significantly (p<0.001) PS exposure in O RBCs after subsequent addition of fresh AB serum (D, G) or simultaneous addition of fresh AB serum (E, G), but not after subsequent addition of i.a. AB serum (F). (***) p<0.001.