FHR-5 Serum Levels and CFHR5 Genetic Variations in Patients With Immune Complex-Mediated
Membranoproliferative Glomerulonephritis and C3-Glomerulopathy
Factor H-related protein 5 (FHR-5) is a member of the complement Factor H protein
family. Due to the homology to Factor H, the main complement regulator of the alternative
pathway, it may also be implicated in the pathomechanism of kidney diseases where
Factor H and alternative pathway dysregulation play a role. Here, we report the first
observational study on CFHR5 variations along with serum FHR-5 levels in immune complex-mediated
membranoproliferative glomerulonephritis (IC-MPGN) and C3 glomerulopathy (C3G) patients
together with the clinical, genetic, complement, and follow-up data.A total of 120
patients with a histologically proven diagnosis of IC-MPGN/C3G were enrolled in the
study. FHR-5 serum levels were measured in ELISA, the CFHR5 gene was analyzed by Sanger
sequencing, and selected variants were studied as recombinant proteins in ELISA and
surface plasmon resonance (SPR).Eight exonic CFHR5 variations in 14 patients (12.6%)
were observed. Serum FHR-5 levels were lower in patients compared to controls. Low
serum FHR-5 concentration at presentation associated with better renal survival during
the follow-up period; furthermore, it showed clear association with signs of complement
overactivation and clinically meaningful clusters.Our observations raise the possibility
that the FHR-5 protein plays a fine-tuning role in the pathogenesis of IC-MPGN/C3G.