title: Bile salt export pump-reactive antibodies form a polyclonal, multi-inhibitory response in antibody-induced bile salt export pump deficiency.
abstract: Progressive familial intrahepatic cholestasis type 2 (PFIC-2) is caused by mutations in ABCB11, encoding the bile salt export pump (BSEP). In 2009, we described a child with PFIC-2 who developed PFIC-like symptoms after orthotopic liver transplantation (OLT). BSEP-reactive antibodies were demonstrated to account for disease recurrence. Here, we characterize the nature of this antibody response in 7 more patients with antibody-induced BSEP deficiency (AIBD). Gene sequencing and immunostaining of native liver biopsies indicated absent or strongly reduced BSEP expression in all 7 PFIC-2 patients who suffered from phenotypic disease recurrence post-OLT. Immunofluorescence, western blotting analysis, and transepithelial transport assays demonstrated immunoglobulin (Ig) G-class BSEP-reactive antibodies in these patients. In all cases, the N-terminal half of BSEP was recognized, with reaction against its first extracellular loop (ECL1) in six sera. In five, antibodies reactive against the C-terminal half also were found. Only the sera recognizing ECL1 showed inhibition of transepithelial taurocholate transport. In a vesicle-based functional assay, transport inhibition by anti-BSEP antibodies binding from the cytosolic side was functionally proven as well. Within 2 hours of perfusion with antibodies purified from 1 patient, rat liver showed canalicular IgG staining that was absent after perfusion with control IgG.
  
  
  CONCLUSIONS
  PFIC-2 patients carrying severe BSEP mutations are at risk of developing BSEP antibodies post-OLT. The antibody response is polyclonal, targeting both extra- and intracellular BSEP domains. ECL1, a unique domain of BSEP, likely is a critical target involved in transport inhibition as demonstrated in several patients with AIBD manifest as cholestasis.
authors.affiliation: Department of Gastroenterology, Hepatology and Infectious Diseases, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Stindt
authors.affiliation: Department of Gastroenterology, Hepatology and Infectious Diseases, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Kluge
authors.affiliation: Department of Gastroenterology, Hepatology and Infectious Diseases, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany.
authors.forename: Carola
authors.initials: C
authors.lastname: Dröge
authors.affiliation: Department of Gastroenterology, Hepatology and Infectious Diseases, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany.
authors.forename: Verena
authors.initials: V
authors.lastname: Keitel
authors.affiliation: Department of Gastroenterology, Hepatology and Infectious Diseases, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Stross
authors.affiliation: Pediatric Gastroenterology and Hepatology, Department for Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School, Hannover, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Baumann
authors.affiliation: Pediatric Hepatology and Liver Transplantation, Transplantation Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Brinkert
authors.affiliation: Pediatric Liver Center, King's College Hospital, London, United Kingdom.
authors.forename: Anil
authors.initials: A
authors.lastname: Dhawan
authors.affiliation: Department of General Pediatrics, Heidelberg University Hospital, Heidelberg, Germany.|Pediatric Clinic, Lukaskrankenhaus GmbH, Neuss, Germany.
authors.forename: Guido
authors.initials: G
authors.lastname: Engelmann
authors.affiliation: Pediatric Hepatology and Liver Transplantation, Transplantation Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.|Clinic of General Pediatrics, University Hospital, Bonn, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Ganschow
authors.affiliation: Department for Pediatric Nephrology, Gastroenterology, Endocrinology and Transplant Medicine, Clinic for Pediatrics II, University Children's Hospital Essen, University Duisburg-Essen, Essen, Germany.|Children's Hospital, Albert Ludwigs University, Freiburg, Germany.
authors.forename: Patrick
authors.initials: P
authors.lastname: Gerner
authors.affiliation: Pediatric Hepatology and Liver Transplantation, Transplantation Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Enke
authors.initials: E
authors.lastname: Grabhorn
authors.affiliation: Institute of Liver Studies, King's College Hospital, London, United Kingdom.
authors.forename: A S
authors.initials: AS
authors.lastname: Knisely
authors.affiliation: Clinical Laboratory Services Division, Dhahran Health Center, Dhahran, Saudi Arabia.
authors.forename: Khalid A
authors.initials: KA
authors.lastname: Noli
authors.affiliation: Latvian Center of Pediatric Gastroenterology/Hepatology, University Children's Hospital, Riga, Latvia.
authors.forename: Ieva
authors.initials: I
authors.lastname: Pukite
authors.affiliation: Texas Children's Hospital Liver Center, Baylor College of Medicine, Gastroenterology, Houston, TX.
authors.forename: Ross W
authors.initials: RW
authors.lastname: Shepherd
authors.affiliation: Pediatric Surgery/Pediatric Liver and GI Transplant, Osaka University Graduate School of Medicine, Osaka, Japan.
authors.forename: Takehisa
authors.initials: T
authors.lastname: Ueno
authors.affiliation: Institute of Biochemistry, Heinrich Heine University, Düsseldorf, Germany.
authors.forename: Lutz
authors.initials: L
authors.lastname: Schmitt
authors.affiliation: Department of Otorhinolaryngology (ENT), Heinrich Heine University School of Medicine, Düsseldorf, Germany.
authors.forename: Constanze
authors.initials: C
authors.lastname: Wiek
authors.affiliation: Department of Otorhinolaryngology (ENT), Heinrich Heine University School of Medicine, Düsseldorf, Germany.
authors.forename: Helmut
authors.initials: H
authors.lastname: Hanenberg
authors.affiliation: Department of Gastroenterology, Hepatology and Infectious Diseases, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany.
authors.forename: Dieter
authors.initials: D
authors.lastname: Häussinger
authors.affiliation: Department of Gastroenterology, Hepatology and Infectious Diseases, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany.|Medical Clinic I, Bethanien Hospital, Moers, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Kubitz
mesh_terms: D000074020:ATP Binding Cassette Transporter, Subfamily B, Member 11; D018528:ATP-Binding Cassette Transporters / Q000172:deficiency* / Q000276:immunology*; D000293:Adolescent; D000906:Antibodies / Q000097:blood*; D002648:Child; D002780:Cholestasis, Intrahepatic / Q000097:blood* / Q000235:genetics / Q000276:immunology*; D005260:Female; D006801:Humans; D016031:Liver Transplantation; D008297:Male; D009154:Mutation; D011183:Postoperative Complications / Q000097:blood* / Q000235:genetics / Q000276:immunology*; D055815:Young Adult
chemical_list: C093491:ABCB11 protein, human; D000074020:ATP Binding Cassette Transporter, Subfamily B, Member 11; D018528:ATP-Binding Cassette Transporters; D000906:Antibodies