Antimitochondrial antibody and primary biliary cirrhosis: can there be one without the other?

Detection of anti-mitochondrial 2-oxoacid dehydrogenase complex subunit's antibodies for the diagnosis of primary biliary cholangitis

Anti-mitochondrial antibodies (AMA), directed against the E2 subunits of the 2-oxo acid dehydrogenase complexes, are markers of Primary Biliary Cholangitis (PBC), a chronic autoimmune liver disease. However, the clinical significance of subunits-specific AMA type PDC-E2 -E2 subunit of the pyruvate dehydrogenase complex-, BCOADC-E2 -E2 subunit of the branched-chain 2-oxo acid dehydrogenase complex-, OGDC-E2 -E2 subunit of the 2-oxo-glutarate dehydrogenase complex- and nPDC -native pyruvate dehydrogenase complex (M2-AMA) . Is not well known, and not all AMA specificities are associated with PBC. The aim of the study was to show the usefulness of the number and combination of subunits-specific AMA positive for the diagnosis of PBC. We detected AMA by indirect immunofluorescence (IIF-AMA) and M2-AMA by dot-blot. We studied the relationship of AMA with some clinical and laboratory variables in 307 patients (37% PBC) with positive dot-blot for M2-AMA. In PBC patients, we detected different E2 subunits of the 2-oxo acid dehydrogenase complexes antibodies (M2-AMA): 82.9% were specific for nPDC, 64.5% for PDC-E2, 44.4% for BCOADC-E2, and 9.6% for OGDC-E2. IIF and dot-blot tests achieved a Area Under the Receiver Operating Characteristic Curve (ROC AUC) of 0.674 (1: 320 cut-off titer, Sensibility (Se) 64.7%, Specificity (Sp) 63.4%) and 0.663 (three specificities M2-AMA, Se 43%, Sp 81.2%), respectively. The detection of different E2 subunits of the 2-oxo acid dehydrogenase complexes antibodies (M2-AMA) by dot-blot showed different ROC AUC: anti-PDC-E2 showed an AUC of 0.610, a Se of 43.7%, and a Sp of 76.4%. Finally, the combined detection of nPDC/BCOADC-E2/PDC-E2 reached an AUC of 0.6095, a Se of 59.6%, and a Sp of 70.2%.The identification of two M2-AMA specificities through dot-blot increased PBC odds ratio (OR) by 2.05 (p:0.031), as compared to the identification of one specificity. Moreover, the identification of three and four specificities increased OR by 4.63 (p:0.000) and by 21.53 (p:0.006), respectively. nPDC/OGDC-E2/PDC-E2 and nPDC/OGDC-E2/BCOADC-E2/PDC-E2 combinations increased PBC OR by 10.04 (p:0.034), as compared to any other combination. 1:320 and 1:640 IIF-AMA increased PBC OR by 4.93 (p:0.009) and 7.67 (p:0.001), respectively, as compared to IIF-AMA titers equal to or less than 1:160. M2-AMA dot-blot was less sensitive but more specific than IIF-AMA, with similar predictive capacity for PBC. Increased numbers of M2-AMA specificities clearly increased the risk of PBC. Some combinations were strongly related to PBC (nPDC/BCOADC-E2/PDC-E2), but others were not (one single M2-AMA, and nPDC plus PDC-E2). M2-AMA dot-blot was less sensitive but more specific than IIF-AMA, with similar predictive capacity for PBC. Increased numbers of M2-AMA specificities clearly increased the risk of PBC, being some combinations, such as nPDC/BCOADC-E2/PDC-E2, more related to PBC than others. Finally, the determination of the number of M2-AMA specificities was more useful than the particular subunit target for PBC diagnosis. In conclusion, the study of the number of M2-AMA specificities by dot-blot should definitely be considered for PBC diagnosis.

Immunohistochemical differences in the portal tract and acinar infiltrates between primary biliary cirrhosis and autoimmune cholangitis

BACKGROUND

Antimitochondrial antibody-negative primary biliary cirrhosis, or autoimmune cholangitis, may be indistinguishable clinically and histologically from antimitochondrial antibody-positive primary biliary cirrhosis.

AIMS

We aimed to compare the phenotypic markers of the portal and acinar infiltrates in autoimmune cholangitis and antimitochondrial antibody-positive primary biliary cirrhosis.

PATIENTS AND METHODS

Formalin-fixed, paraffin-embedded liver sections were identified from 32 patients with a clinical and histological diagnosis of primary biliary cirrhosis. Thirteen were antimitochondrial antibody-negative (autoimmune cholangitis group) and 19 were antimitochondrial antibody-positive. The groups were well matched for age, histological stage, liver biochemistry and drug treatment. Immunohistochemical staining was performed using monoclonal antibodies against CD3 (pan T cell), CD8 (cytotoxic), CD45RO (memory), CD45RA (naive), CD68 (macrophages) and against the secreted form of eosinophilic cationic protein (EG2).

RESULTS

In autoimmune cholangitis, both portal and acinar CD3 cell counts were significantly higher than in antimitochondrial antibody-positive primary biliary cirrhosis (median portal count 421 vs 257 cells/graticule, P< 0.03; median acinar count 18 vs 9 cells/graticule, P< 0.02). There were no differences between the groups in portal or lobular CD8, CD45RO, CD45RA, CD68 or EG2. Of the total group (antimitochondrial antibody positives and negatives), there were significantly more CD45RA cells in early (stage 1) compared with cirrhotic (stage 4) disease (median 19.3 vs 14 cells/graticule, P< 0.03). EG2 staining was found in eight of the 32 sections overall, but not in the patients with stage 1 disease (P< 0.04).

CONCLUSION

CD3 counts are higher in autoimmune cholangitis than in antimitochondrial antibody-positive primary biliary cirrhosis in both portal and acinar areas. However, there are no significant differences in memory/naïve T-cell subsets between both conditions and, in both, loss of naive T lymphocytes and secretion of eosinophilic cationic protein occur with disease progression. This implies that the effector pathways of bile duct destruction are similar in autoimmune cholangitis and primary biliary cirrhosis.

Changes in titers of antimitochondrial and antinuclear antibodies during the course of primary biliary cirrhosis

A case of primary biliary cirrhosis (PBC) in whom a complete biochemical (serum bilirubin, transaminases and alkaline phosphatase) remission was noted after combination treatment with ursodeoxycholic acid (UDCA) and corticosteroid is reported. The antimitochondrial antibody (AMA) detected by indirect immunofluorescence was initially positive, and the antinuclear antibody (ANA) was negative, but these two antibodies subsequently fluctuated independently (AMA-positive/ANA-negative, AMA-negative/ANA-negative, AMA-negative/ANA-positive, AMA-positive/ANA-positive, and again AMA-negative/ANA-positive) in spite of a lack of histopathological improvement in the liver after treatment. The clinical presentation in our case suggests that in some cases the diagnosis of PBC or so-called autoimmune cholangitis (AIC) might depend on the 'phase' of the same disease. Our results also suggest that detailed immunoreactive profiles against 2-oxo-acid dehydrogenase complex (2-OADC) enzymes by using immunoblotting, together with a serial histological examination, should provide more precise information for a diagnosis of PBC.

Recurrent primary biliary cirrhosis

Transplantation has become the accepted form of therapy for patients with end-stage liver disease. The diagnosis of recurrent disease in the allograft has been a matter of controversy, partly because of the difficulties in making the diagnosis in the allograft situation. The conventional criteria for diagnosing PBC may be inappropriate and there are many causes of bile duct damage in the graft. That the PBC-specific autoantibodies [such as antimitochondrial antibody (AMA) and gp-210] persist after transplantation is universally found, and some have reported the aberrant distribution of E2 in the allograft that is typical of PBC in the native liver, whether or not there is histological evidence of PBC recurrence. Most studies now accept that histological features of PBC, such as granulomatous bile duct damage, ductopenia and biliary-type fibrosis, may be found in the allograft; the histological features of PBC are variable and do not mirror the liver tests. The rate of recurrence increases with time, so that by 10 years, recurrence may be found in 30-50% of biopsies. There are no clear factors which identify those at risk of recurrence, but the pattern and degree of immunosuppression may be implicated. Cirrhosis has only rarely been reported. In the medium term, recurrence of PBC has little clinical impact. Ursodeoxycholic acid is used in some centres but there is no clear evidence for benefit.

Antibody to carbonic anhydrase II is present in primary biliary cirrhosis (PBC) irrespective of antimitochondrial antibody status

Antibody to carbonic anhydrase II, an enzyme abundantly present in biliary epithelium, has been proposed as a diagnostic marker for antimitochondrial antibody-negative PBC. In this study we determine its prevalence and clinical significance in a large series of patients with antimitochondrial antibody-positive and -negative PBC. Reactivity to carbonic anhydrase II was sought by Western immunoblotting in sera from 215 consecutive patients with PBC (26 antimitochondrial antibody-negative), 13 with autoimmune hepatitis, 25 with primary Sjögren's syndrome (pSS), 12 with systemic sclerosis, 19 with systemic lupus erythematosus and 73 healthy subjects. The prevalence of antibody to carbonic anhydrase II (titre 1:100) in PBC was 8%. No specific reactivity to carbonic anhydrase II was found in antimitochondrial antibody-negative PBC (7% versus 8% in antimitochondrial antibody-positive PBC). Ascites (P = 0.006) and Sjögren's syndrome (SS) (P = 0.022) in PBC were significantly associated with presence of the antibody. In patients with SS associated with PBC, the prevalence (19%) was similar to that observed in pSS (16%). At a serum dilution of 1:40, the prevalence of positive sera in PBC rose to 27% but disease specificity was reduced. Our findings in a large population of PBC patients rule out a relation between presence of antibody to carbonic anhydrase II and lack of antimitochondrial antibody. The higher prevalence of ascites found in positive patients warrants further evaluation.