In apparent contrast with what we have observed in vivo in patients on eculizumab, in untreated PNH patients (n = 14) a similar proportion of C3+ PNH RBCs was observed among both reticulocytes and non-reticulocytes (Fig. 5b) after in vitro incubation with acidified sera with eculizumab (Fig. 5c: 45.6 vs. 37.1%). The gene discussed is C3; the disease is paroxysmal nocturnal hemoglobinuria.