Decreased formation of the complement component C4A in leukocyte-depleted stored whole blood.

As reported earlier, factors of the complement cascade get activated in CPD-A1-stabilized whole blood. While leukocyte depletion inhibited partially the activation of C4, it had no effect on C3a concentrations. Therefore cleavage of C4 during storage of whole blood seems to be partially leukocyte-dependent, whereas the activation of C3 is possibly due to the activation of the alternate pathway of the complement system by contact of blood to plastic surfaces. Even though the radioimmunologically measured C3a might be inactive as an anaphylatoxin, these observations are of clinical importance since the inactivated C3a-desArg still possesses biological activities, like activation of platelets which may lead to hypercoagulability and thrombosis.