Generation of fluid phase C3a (A) and sC5b-9 (B) binding of C3 fragments to the biomaterial surface (C), and expression of CD11b on circulating PMNs in whole blood (D) during incubation in the tubing loop model. Whole blood containing 0.4 IU of heparin/mL in the presence (squares) or absence (circles) of 43 μmol/L Compstatin (an eightfold molar excess over C3) was rotated up to 60 minutes at 37°C in PVC tubing loops filled with 5 mL fluid (4 mL of gas). Open symbols represent experiments performed with 10 mmol/L EGTA, and filled symbols represent those without EGTA present.