PEG-modified RBCs are resistant to antibody binding.

Control and PEG-modified RBCs were assessed by flow cytometry using a FITC-labeled murine antihuman glycophorin A antibody. There is a dose-dependent inhibition of antibody binding to RBCs treated with varying concentrations of both the 3.35 kd PEG derivative (■) and the 18.5 kd PEG derivative (▪). Error bars indicate the standard deviation of 3 determinations. Percentage inhibition of binding was determined by comparing peak mean fluorescence of PEG-modified RBCs to control RBCs as follows: Control RBCs − PEG RBCs/Control RBCs × 100.