Abstract: TH-PO1077
Screening of Complement-Mediated Thrombotic Microangiopathies Using an Endothelial C5b9 Deposition Assay
Session Information
- Pathology and Lab Medicine
October 22, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Pathology and Lab Medicine
- 1700 Pathology and Lab Medicine
Authors
- Badie, Amandine, Centre de Recherche du Centre Hospitalier Universitaire Sainte-Justine, Montreal, Quebec, Canada
- Sahu, Srishti, Centre de Recherche du Centre Hospitalier Universitaire Sainte-Justine, Montreal, Quebec, Canada
- Mathieu, Hélène, Centre de Recherche du Centre Hospitalier Universitaire Sainte-Justine, Montreal, Quebec, Canada
- Lapeyraque, Anne-Laure, Centre Hospitalier Universitaire Sainte-Justine, Montreal, Quebec, Canada
- Bonnefoy, Arnaud, OPTILAB Montreal, Department of Clinical Laboratory Medicine, Montreal, Quebec, Canada
- Alexandra, Cambier, Centre Hospitalier Universitaire Sainte-Justine, Montreal, Quebec, Canada
Group or Team Name
- Laboratory of Dr. Cambier
Background
Thrombotic microangiopathies (TMAs) are clinical syndromes characterized by endothelial injury and microthrombus formation, with renal involvement that may progress to kidney failure. The central role of complement system overactivation in the pathophysiology of certain TMAs is well established, notably through C5b9 deposition on the vascular endothelium. To date, no specific and sensitive biomarker is available to assess this activation in all patients; however, detection of endothelial C5b9 deposition represents a promising approach.
The objective of this study was to assess the ability of our assay to detect dysregulated complement activation in sera of patients with suspected TMA. We are developing this test in compliance with ISO 15189 requirements, toward clinical implementation in Quebec.
Methods
HMEC-1 endothelial cells were incubated with sera from six patients with suspected TMA (1.5-38 years), including three untreated patients (one of whom was evaluated before and after treatment with eculizumab) and three patients treated with complement inhibitors (eculizumab or ravulizumab). Sera from fifteen healthy patients were used as controls. Endothelial C5b9 deposits were detected by immunofluorescence and analyzed by microscopy. The percentage of endothelial surface positive for C5b9 staining was quantified and normalized to a control serum.
Results
Among the six patients suspected of TMA, serum from one untreated patient induced C5b9 deposits on endothelial cells, exceeding the threshold defined using control sera. In contrast, following treatment with complement inhibitors, serum from this patient and from three additional patients did not induce significant C5b9 deposits, with a percentage below the threshold.
Conclusion
Our results demonstrate that assessment of endothelial C5b9 deposition enables detection of terminal complement activation in patients with suspected TMA and may represent a functional tool to monitor the efficacy of complement inhibitor therapies. This assay represents a step toward the standardization of an additional approach to support TMA diagnosis.
Funding
- Commercial Support – Alexion Canada