Supplementary Material for: Immunological Characteristics of Chinese Adult Patients with Anti-Complement Factor H Autoantibodies Associated Complement-Mediated Thrombotic Microangiopathy

Background Anti-complement factor H autoantibodies (FHAAs) associated complement-mediated thrombotic microangiopathy (CM-TMA) is prevalent in pediatric patients and plays an important role in the pathogenesis of CM-TMA. The epitopes of FHAAs in adult CM-TMA patients still remain to be further explored. Methods A total of 114 adult patients with CM-TMA were enrolled. Their clinicopathological data as well as plasma samples were collected. 7 CFH fragments covering different short consensus repeats (SCRs) of factor H were expressed by HEK293 or ExpiCHO cells. The presence of FHAAs and the antigen epitopes were detected by using enzyme linked immunosorbent assay. Results FHAAs were detected in 10 of the adult patients with CM-TMA. The main epitope of FHAAs was SCRs15-20 (88.89%, 8/9). The prevalence of anti-SCRs1-4, anti-SCRs1-6, anti-SCRs5-7, anti-SCR7, anti-SCRs11-14, and anti-SCRs19-20 autoantibodies was 22.22% (2/9), 0% (0/9), 33.33% (3/9), 11.11% (1/9), 0% (0/9), and 44.44% (4/9), respectively. The levels of anti-SCRs15-20 autoantibodies were significantly decreased in the remission phase compared with that in the active phase (107.49 ± 36.8 AU/mL vs. 181.52 ± 33.62 AU/mL, P = 0.04). Malignant hypertension was found in 60% (6/10) patients with FHAA-associated CM-TMA. 80% (8/10) of these patients had a poor prognosis, including 5 with end-stage kidney disease, 2 with renal transplantation, and 1 patient who died. Conclusion FHAAs were positive in 8.77% (10/114) of adult CM-TMA patients and SCRs15-20 might be the main epitope of FHAAs in FHAA-associated CM-TMA.