Detection of antimitochondrial autoantibodies in immunofluorescent AMA-negative patients with primary biliary cirrhosis using recombinant autoantigens.
Antimitochondrial antibodies (AMA) are the serologic hallmark of primary biliary cirrhosis (PBC). However, depending on the clinical laboratory, from 5% to 17% of PBC patients are consistently AMA-negative, using native mitochondrial antigens and a variety of conventional assays including immunofluorescence (IMF) and enzyme-linked immunosorbent assay (ELISA). The major immunoreactive mitochondrial autoantigens are the E2 members of the 2-oxo-acid dehydrogenase complex family, including pyruvate dehydrogenase complex-E2 (PDC-E2), branched chain 2-oxo acid dehydrogenase complex-E2 (BCOADC-E2), and oxo-glutarate dehydrogenase complex-E2 (OGDC-E2); cDNAs of these proteins have now been cloned, sequenced, and their B-cell epitopes defined. In the present study, we cloned cDNAs encoding these proteins from human, not bovine, sources, and expressed the recombinant proteins in a newly developed ELISA that employs a unique Escherichia coli buffer, and compared the data with previous assays using both AMA-positive and -negative patients. Using this new assay and our criteria for positive as an optical density (OD) greater than 10 SD above the mean of control sera, the AMA-positive rate of 191 PBC sera was 94% (179 of 191) compared with 84% (161 of 191) by IMF. None of the 316 control sera were reactive. Using our recombinant assays, we focused attention on the 30 IMF-AMA-negative patients. Twenty-two of 30 (73%) of these patients were positive using this new ELISA. The group of 30 IMF-AMA-negative/ELISA-positive patients did not differ significantly from a comparable population of IMF-AMA-positive patients with respect to age, sex distribution, liver function tests, elevation of serum IgM, or pathologic stage.
Miyakawa
H
H
Fourth Department of Internal Medicine, Teikyo University School of Medicine, Kanagawa, Japan.
Tanaka
A
A
Kikuchi
K
K
Matsushita
M
M
Kitazawa
E
E
Kawaguchi
N
N
Fujikawa
H
H
Gershwin
M E
ME
D001323:Autoantibodies / Q000032:analysis*; D001324:Autoantigens / Q000276:immunology*; D015153:Blotting, Western; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D008105:Liver Cirrhosis, Biliary / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D008928:Mitochondria / Q000276:immunology*; D011994:Recombinant Proteins; D012680:Sensitivity and Specificity
D001323:Autoantibodies; D001324:Autoantigens; D000939:Epitopes; D011994:Recombinant Proteins