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Updated: Sep 17, 2025
Methods for Quantitative Detection of Antibody-induced Complement Activation on Red Blood Cells
Published on: January 29, 2014
In Vitro Evaluation of the Inhibitory Effects of Eculizumab and C1 Esterase Inhibitor on Human and Rhesus Monkey
Tianyi Hu1, Hao Feng1, Man Zhang1
1Institute of Organ Transplantation, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Key Laboratory of Organ Transplantation, Ministry of Education, NHC Key Laboratory of Organ Transplantation, Key Laboratory of Organ Transplantation, Chinese Academy of Medical Sciences, Organ Transplantation Clinical Medical Research Center of Hubei Province, Wuhan, China.
Background:
Complement inhibitors are important therapeutic drugs after xenotransplantation. However, it is still unclear whether the commonly used clinical complement inhibitors eculizumab and C1 esterase inhibitor (C1-INH) can effectively inhibit complement activation in nonhuman primates.
Methods:
The anti-complement activities of eculizumab and C1-INH were evaluated using an in vitro model of normal human serum (NHS) or normal rhesus monkey serum (NRS)-mediated complement-dependent cytotoxicity (CDC), with an immortalized porcine aortic endothelial cell line (iPEC) as the target.
Results:
Pretreatment of the NHS with various doses of eculizumab potently inhibited the cell lysis of iPECs. FACS analysis showed that eculizumab potently suppressed the deposition of C5b-9, but not C3c and C4c, on iPECs. However, although eculizumab pretreatment of the NRS had a dose-dependent inhibitory effect on the killing of iPECs, the effect was much weaker than that for similarly treated NHS. Pretreatment of NHS and of NRS with C1-INH produced almost identical dose-dependent inhibitory effects on the killing of iPECs. At the highest concentration (10 IU/mL) of C1-INH used, the CDC was reduced by only about 75%. In addition, C1-INH had moderate inhibitory effects on the deposition of C3c, C4c, and C5b-9 in both humans and rhesus monkeys. When C1-INH was given intravenously to rhesus monkeys at a dose of 17.5 IU/kg, the serum-mediated cell lysis detected in vitro was only slightly reduced, and the maximum inhibition was about 20%.
Conclusion:
The inhibitory effect of eculizumab on human complement was significantly stronger than it was on rhesus monkey complement, showing obvious species specificity. The inhibitory effect of C1-INH on complement in humans and rhesus monkeys was similar, but a higher concentration of C1-INH was required in monkeys to achieve a significant inhibitory effect. These results provide a reference basis for the selection of complement inhibitors after clinical or preclinical xenotransplantation.
