In the present study, immunoproteomic analysis was utilized to systemically characterize global
autoantibody profiles in
autoimmune hepatitis (AIH). Sera from 21 patients with AIH and 15 healthy controls were analyzed for the antibody reactivity against the
protein antigens of HepG2, a human
hepatoma cell line. The lysates of HepG2 cells were separated by two-dimensional electrophoresis and then immunoblotted with each serum sample. Matrix-assisted
laser desorption/ionization mass spectrometry or/and nanoelectrospray ionization MS/MS were then used to identify
antigens, among which a bifunctional
enzyme in mitochondrial,
fumarate hydratase (FH), was further analyzed by ELISA using recombinant FH as a coating
antigen. A total of 18 immunoreactive spots were identified as 13
proteins, 8 of which have not been reported in AIH. Immune reactivity to FH was detected in 66.67% of patients with AIH, 19.35% of patients with
primary biliary cirrhosis (PBC), 12.31% of patients with
chronic hepatitis B (CHB), 6.35% of patients with
chronic hepatitis C (CHC), 11.32% of patients with
systemic lupus erythematosus (SLE), and 3.57% of normal individuals. The differences of prevalence between AIH patients and healthy controls as well as other diseases were of statistical significance (P<0.001). These data demonstrate the serological heterogeneity in AIH and suggest the diversity of the mechanisms underlying AIH. FH, recognized mainly in AIH rather than in viral
hepatitis and other
autoimmune diseases, may have utility in improved diagnosis of AIH.