ACTIVATION OF THE COMPLEMENT-SYSTEM BY RADIOGRAPHIC CONTRAST-MEDIA - STUDIES INVIVO AND INVITRO

The effect of radiographic contrast media (RCM) on the complement system was studied in vivo and in vitro. In 65 patients undergoing intravenous pyelography, plasma was obtained before and 3, 5, 10, 20, 30, and 60 min postinfusion. Nine patients experienced immediate generalized reactions (IGR) post-RCM infusions. Six patients developed urticaria, 1 developed angioedema, and 2 developed nausea and hypotension. A significant decrease in CH50 occurred in 29 patients, including 6 with IGR. Split products of C3 were detected in 24 of these patients. Six patients without change in CH50 had detectable C3 split products. There was a statistically significant decrease in hemolytically active C3 and factor B, but not C1q or C4 in the group with decreased CH50 when compared to the group without CH50 change. All patients had normal levels of C1 esterase inhibitor, C3aI (serum carboxypeptidase B), C3bI, and βIH. Neither anti-RCM antibodies nor immune complexes were detected in any patient's plasma. In vitro, decreased CH50 and hemolytically active C4, C3, properdin, and factor B were found with incubation of plasma with RCM. These changes occurred independent of the buffer used (EDTA/EGTA). Finally, C3 split products were detected in the reaction mixtures. These data indicate that RCM is associated with decreased hemolytic complement activity, both in vivo and in vitro. Furthermore, the in vitro changes occurred without the presence of calcium or magnesium, indicating that complement activation by RCM may occur in a nonsequential manner. © 1979.