Fig 2: (A) Factor H-related protein 5 (FHR-5) protein levels in the previously described clusters of C3 glomerulopathy (C3G)/immune complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) patients (19, 37). The clinically meaningful clusters were generated based on clinical, histological, genetic, and complement data of patients as described by Iatropoulos et al. (19). Each dot represents one patient. 1p-value was determined with ANOVA for patients without CFHR5 variations comparing patients in clusters 1, 3, and 4. *p < 0.05 by Dunn’s posttest, for patients without CFHR5 variations. (B) C3 and FHR-5 levels according to cluster membership and the presence of CFHR5 variations.

Fig 3: (A) Comparison of serum Factor H-related protein 5 (FHR-5) levels and serum FHR-5 C3b-binding ability of patients with only FHR-5WT and those carrying FHR-5G278S or FHR-5R356H in ELISA. C3b was immobilized, then serum was added, and FHR-5 was detected by polyclonal anti-FHR-5. Dots represent individual patients. Data are mean of two measurements and are normalized to a calibrator sample containing only FHR-5WT. Subjects expressing FHR-5G278S show a tendency of lower FHR-5 levels and decreased C3b binding compared to the FHR-5WT-expressing group. Serum FHR-5 levels were measured in a sandwich ELISA. Circles represent individual patients. Data are mean of two measurements. (B) Dose-dependent binding of recombinant FHR-5WT, FHR-5G278S, and FHR-5R356H to purified C3b measured in ELISA. The FHR-5G278S variant binds significantly weaker to C3b (one-way ANOVA with Bonferroni’s posttest, p < 0.01). Data are mean of four measurements ± SEM. (C) Interaction of C3b–FHR-5 variants measured by surface plasmon resonance (SPR). C3b in serial dilutions was flown over immobilized FHR-5 variants. The KD of the C3b–FHR-5G278S is one order greater compared to that of C3b–FHR-5R356H and C3b–FHR-5WT. Data are representative of two experiments.

Fig 4: Factor H-related protein 5 (FHR-5) on Western blot. Two serum samples obtained from patients with wild-type FHR-5 protein were analyzed.

Fig 5: Patients’ Factor H-related protein 5 (FHR-5) and C3 levels along with the presence of CFHR5 variations and end-stage renal disease (ESRD). Dotted lines indicate the threshold of high and low C3 (0.9 g/L) and FHR-5 (1.565 mg/L) levels. Rates of ESRD during follow-up - C3 <0.9 g/L, FHR-5 <1.56 mg/L: 0.032/event/patient/year, median (min–max) follow-up: 1.6 (0.11–6) - C3 <0.9 g/L, FHR-5 >1.56 mg/L: 0.11/event/patient/year, median (min–max) follow-up: 1.5(0.05–6) - C3 >0.9 g/L, FHR-5 <1.56 mg/L: 0/event/patient/year; median (min–max) follow-up: 1.57 (0.21–6) - C3 >0.9 g/L, FHR-5 >1.56 mg/L: 0.099 event/patient/year; median (min–max) follow-up: 1.5 (0.13–6).