title: High prevalence of antibodies to calreticulin of the IgA class in primary biliary cirrhosis: a possible role of gut-derived bacterial antigens in its aetiology?
abstract: BACKGROUND
  In a preliminary study we showed that antibodies to the endoplasmic reticulum protein calreticulin (CR) occur in primary biliary cirrhosis (PBC) and autoimmune hepatitis type 1 (AIH). Since anti-CR antibodies have also been found in patients with infectious diseases, we investigated their prevalence and immunoglobulin classes in patients with various hepatic and intestinal diseases, hoping to get some information on a possible relationship between an infectious trigger and the induction of a certain class of anti-CR antibodies.
  
  
  METHODS
  Sera were tested for anti-CR antibodies of the IgA, IgG, and IgM class by Western blotting, using CR isolated from human liver: in autoimmune liver diseases (primary biliary cirrhosis (PBC) (n = 86) and autoimmune hepatitis (AIH) type 1 (n = 57)), alcoholic liver cirrhosis (ALC) (n = 32), viral liver infections (acute hepatitis A (n = 8), acute hepatitis B (n = 20), and chronic hepatitis C (n = 28)), and intestinal diseases (Crohn disease (CD) (n = 30), acute yersiniosis (n = 26)). Sera from 100 healthy individuals served as negative controls.
  
  
  RESULTS
  The most prominent finding was the high prevalence of anti-CR antibodies of the IgA class and the similarity in the anti-CR antibody class pattern in PBC (IgA, 62%; IgG, 43%; IgM, 55%) and yersiniosis (IgA, 62%; IgG, 39%; IgM, 42%). Class IgA anti-CR antibodies also occurred frequently in ALC (IgA, 44%; IgG, 41%; IgM, 19%). In contrast, in AIH anti-CR antibodies were predominantly of class IgG (IgA, 28%; IgG, 60%; IgM, 33%). In hepatitis A anti-CR antibodies were absent. In the other diseases they had a low prevalence and were mostly of class IgG (acute hepatitis B: IgA, 0%; IgG, 15%; IgM, 0%; chronic hepatitis C: IgA, 7%; IgG, 21%; IgM, 0%; CD: IgA, 13%; IgG, 20%; IgM, 13%). Of the healthy individuals 7% had anti-CR antibodies exclusively of class IgG.
  
  
  CONCLUSIONS
  The high prevalence of anti-CR antibodies of class IgA in patients with PBC and yersiniosis as well as in alcoholic liver disease reflects a reactivity of the gut-associated immune system and could imply that a still undefined gut-derived bacterial (?) agent may trigger PBC.
authors.affiliation: Dept. of Gastroenterology, Hepatology and Endocrinology, Medical Clinic, University of Freiburg, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Kreisel
authors.forename: A
authors.initials: A
authors.lastname: Siegel
authors.forename: A
authors.initials: A
authors.lastname: Bahler
authors.forename: C
authors.initials: C
authors.lastname: Spamer
authors.forename: E
authors.initials: E
authors.lastname: Schiltz
authors.forename: M
authors.initials: M
authors.lastname: Kist
authors.forename: G
authors.initials: G
authors.lastname: Seilnacht
authors.forename: R
authors.initials: R
authors.lastname: Klein
authors.forename: P A
authors.initials: PA
authors.lastname: Berg
authors.forename: C
authors.initials: C
authors.lastname: Heilmann
mesh_terms: D000942:Antigens, Bacterial / Q000276:immunology*; D001323:Autoantibodies / Q000097:blood*; D001324:Autoantigens / Q000276:immunology* / Q000302:isolation & purification; D015153:Blotting, Western; D002135:Calcium-Binding Proteins / Q000276:immunology* / Q000302:isolation & purification; D037282:Calreticulin; D003424:Crohn Disease / Q000276:immunology; D006505:Hepatitis / Q000276:immunology; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D008104:Liver Cirrhosis, Alcoholic / Q000276:immunology; D008105:Liver Cirrhosis, Biliary / Q000276:immunology* / Q000382:microbiology*; D012261:Ribonucleoproteins / Q000276:immunology* / Q000302:isolation & purification; D015009:Yersinia Infections / Q000276:immunology
chemical_list: D000942:Antigens, Bacterial; D001323:Autoantibodies; D001324:Autoantigens; D002135:Calcium-Binding Proteins; D037282:Calreticulin; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D012261:Ribonucleoproteins