Anti factor H autoantibodies block C-terminal recognition function of factor H in hemolytic uremic syndrome.
The atypical form of the kidney disease hemolytic uremic syndrome (aHUS) is associated with defective complement regulation. In addition to mutations in complement regulators, factor H (FH)-specific autoantibodies have been reported for aHUS patients. The aim of the present study was to understand the role of these autoantibodies in aHUS. First, the binding sites of FH autoantibodies from 5 unrelated aHUS patients were mapped using recombinant FH fragments and competitor antibodies. For all 5 autoantibodies, the binding site was localized to the FH C-terminus. In a functional assay, isolated patient IgG inhibited FH binding to C3b. In addition, autoantibody-positive patients' plasma caused enhanced hemolysis of sheep erythrocytes, which was reversed by adding FH in excess. These results suggest that aHUS-associated FH autoantibodies mimic the effect of C-terminal FH mutations, as they inhibit the regulatory function of FH at cell surfaces by blocking its C-terminal recognition region.
Józsi
Mihály
M
Junior Research Group Cellular Immunobiology, Leibniz Institute for Natural Product Research and Infection Biology, Hans Knöll Institute, Jena, Germany. mihaly.jozsi@hki-jena.de
Strobel
Stefanie
S
Dahse
Hans-Martin
HM
Liu
Wei-shih
WS
Hoyer
Peter F
PF
Oppermann
Martin
M
Skerka
Christine
C
Zipfel
Peter F
PF
D000818:Animals; D001323:Autoantibodies / Q000737:chemistry / Q000276:immunology*; D001327:Autoimmune Diseases / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D001666:Binding Sites, Antibody / Q000235:genetics / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D003167:Complement Activation / Q000235:genetics / Q000276:immunology*; D003179:Complement C3b / Q000235:genetics / Q000276:immunology; D017242:Complement Factor H / Q000235:genetics / Q000276:immunology*; D004912:Erythrocytes / Q000737:chemistry / Q000276:immunology; D005260:Female; D030342:Genetic Diseases, Inborn / Q000235:genetics / Q000276:immunology / Q000473:pathology; D006461:Hemolysis / Q000276:immunology; D006463:Hemolytic-Uremic Syndrome / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D006801:Humans; D007074:Immunoglobulin G / Q000235:genetics / Q000276:immunology; D008297:Male; D018716:Molecular Mimicry / Q000235:genetics / Q000276:immunology*; D009154:Mutation / Q000276:immunology; D010449:Peptide Mapping; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D017434:Protein Structure, Tertiary / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000276:immunology; D012756:Sheep
D001323:Autoantibodies; D007074:Immunoglobulin G; D011994:Recombinant Proteins; D003179:Complement C3b; D017242:Complement Factor H