The transfer of rhCD59-P between PNH erythrocytes in vitro. Whole PNH blood (A) was incubated with 1850 nM rhCD59-P for 30 minutes at 37°C, followed by a PBS wash to produce “CD59-reconstituted” cells (B). A separate sample of PNH whole blood was diluted 1:100 in PBS and incubated in the presence of serum with the reconstituted cells at 37°C for either 1 minute (C) or 24 hours (D). As a negative control, non-PNH human blood was incubated with 1:100-diluted PNH whole blood for 30 minutes at 37°C (E). Surface levels of human CD59 were measured on all samples by flow cytometry using a fluorescent anti-CD59 antibody.