Generation of fluid-phase C3a (open squares) and sC5b-9 (closed diamonds), binding of C3/C3 fragments (open circles) to the biomaterial surface, and expression of CD11b on circulating PMNs (closed triangles) in whole blood during incubation in the tubing loop model. Whole blood containing 0.4 IU of heparin/mL was rotated for 60 minutes at 37°C in PVC tubing loops filled with 5 mL fluid (4 mL of gas). The peptides were present at concentrations of up to 250 μmol/L (a 46-fold excess when compared with plasma C3). Data are the mean of three experiments and are presented as the mean percentage ± SEM of the values obtained with 250 μmol/L of control peptide.