Fig. 5

C3 binding on young (reticulocytes) and mature (non-reticulocytes) PNH red cells in the presence of eculizumab in vivo and in vitro. Analysis of PNH (CD59-negative) red cells for reticulocyte staining (polymethine dye) and C3 binding in a representative patient whose red cells has been studied both a in vivo (after 6 months of eculizumab treatment: left panel) and b in vitro (before starting eculizumab: right panel). In the in vitro experiment, red cells have been incubated for 2 h with acidified ABO-compatible sera from patients on eculizumab without MgCl₂ addition. Serum acidification has not induced any C3 binding to non-PNH red cells neither with nor without eculizumab (data not shown). c The bar diagram shows the average (+SD) proportion of young (reticulocytes: RET, filled bars) and mature (non-reticulocytes: no-RET, empty bars) PNH (CD59-negative) red cells bound with C3 in patients studied during (from 3 to 36 months from the start) eculizumab treatment (on the left: eculizumab in vivo) and in patients not on eculizumab studied in vitro (on the right: eculizumab in vitro). n: number of different patients. ECU: eculizumab