S. Reynoso-paz et al., Evidence for a locally driven mucosal response and the presence of mitochondrial antigens in saliva in primary biliary cirrhosis, HEPATOLOGY, 31(1), 2000, pp. 24-29
Primary biliary cirrhosis (PBC) is often considered to be a dry gland disea
se caused by frequent involvement of salivary and lacrimal glands. Although
high titers of antimitochondrial autoantibodies (AMA) have long been recog
nized in PBC, little is known about the presence of mitochondrial autoantig
ens in mucosal compartments such as saliva. We investigated saliva and sera
in PBC patients and controls for the presence of AMA and mitochondrial ant
igens. In PBC saliva, AMA were detected in 45 of 49 (92%), with specificity
directed against pyruvate dehydrogenase complex (PDC-E2) alone in 22 of 49
(45%), against PDC-E2 and branched-chain 2-oxo-acid dehydrogenase complex
E2 (BCOADC-E2) in 45 of 49 (8%), to PDC-E2 and 2-oxoglutarate dehydrogenase
complex E2 (OGDC-E2) in 9 of 49 (18%), and to the 3 antigens together in 1
0 of 49 (20%). Isotyping of the saliva AMA showed that 80% of the patients
had immunoglobulin A (IgA) against PDC-E2, 18% had IgM-specific PDC-E2, and
35% had IgG specific PDC-E2. Similar to serum and bile anti-PDC-E2 IgA ant
ibodies, the saliva autoantibodies localized their reactivity to the inner
lipoyl domain of PDC-E2. Furthermore, saliva from patients with PBC but not
controls inhibited pyruvate dehydrogenase enzyme activity in vitro, In add
ition, and of particular interest, we detected a molecule with a molecular
weight corresponding to PDC-E2 (74 kd) in PBC but not control saliva. These
findings make several important points: first, there appears to be localiz
ed mucosal immunity in the secretory system of PBC; second, AMA are readily
detected in PBC saliva; and third, PDC-E2 may be present in the saliva of
PBC.