Microbial mimics are major targets of crossreactivity with human pyruvate dehydrogenase in primary biliary cirrhosis.

BACKGROUND/AIMS: Previous studies on patients with primary biliary cirrhosis (PBC) have shown extensive cross-reactivity between the dominant B- and T-cell epitopes of human pyruvate dehydrogenase complex-E2 (PDC-E2), and microbial mimics. Such observations have suggested microbial infection as having a role in the induction of anti-mitochondrial antibodies, through a mechanism of molecular mimicry. However the biological significance of these cross-reactivities is questionable, because PDC-E2 is so highly conserved among various species. METHODS: Interrogating protein databases, ten non-PDC-E2 microbial sequences with high degree of similarity to PDC-E2(212-226) were found in Escherichia coli (6), Helicobacter pylori, Pseudomonas aeruginosa, Cytomegalovirus, and Haemophilus influenzae. We report on a study testing reactivity and competitive cross-reactivity against these respective peptides, and in some cases the parent protein, using sera from 55 patients with PBC, compared to reactivity of 190 pathological and 28 healthy controls. RESULTS: Cross-reactivity to E. coli mimics was commonly seen in PBC, and in a subset of pathological controls except where there was no evidence of urinary tract infection and correlated with anti-mitochondrial reactivity. CONCLUSIONS: E. coli/PDC-E2 cross-reactive immunity characterizes primary biliary cirrhosis; the large number of E. coli immunogenic mimics may account for the dominance of the major PDC-E2 autoepitope.

Donor liver preservation and stimulation of adhesion molecules : cold preservation initiates the cascade.

BACKGROUND: Pro-inflammatory adhesion molecules (including ICAM-1, E-Selectin) are important in clinical hepatic ischaemia and reperfusion injury. The initiating factors remain to be fully elucidated. METHODS: Needle biopsies taken during and after donor liver preservation were studied in 28 cases by immunohistochemical methods. Human responder cell cultures were exposed to the effluent cold storage solution after liver preservation in a further 10 transplants. RESULTS: Increased ICAM-1 staining was seen at the end of cold storage compared to baseline (P less than 0.01), whilst reperfusion caused further increase (P less than 0.001). The storage solutions stimulated ICAM-1 and E-Selectin expression in responder cells in vitro as a bioassay (P less than 0.01 in each case). CONCLUSIONS: Liver harvesting and cold storage can initiate adhesion molecule expression even before reperfusion in the recipient.

Pro-inflammatory agents accumulate during donor liver cold preservation: a study on increased adhesion molecule expression and abrogation by curcumin in cultured endothelial cells.

Cold hypoxia and re-oxygenation during organ preservation leads to a variety of stresses, including expression of adhesion molecules, which can promote inflammatory responses and compromised function. These studies were undertaken to investigate the pro-inflammatory activities of factors present in the vascular bed at the end of cold storage in livers during clinical hepatic transplantation. Effluent perfusate (termed pro-inflammatory vascular effluent-PVE) washed out at the end of cold storage, was collected from 10 donor livers, and used in a bio-assay with cultured endothelial cells exposed to cold hypoxia and re-oxygenation. Adhesion molecule expressions for intercellular adhesion molecule 1 (ICAM-1) and E-selectin were measured using molecular techniques and Northern blot analyses. Cells exposed to PVE during warming showed up-regulation of both ICAM-1 and E-selectin (p<0.05 in both cases) in all 10 preparations. Addition of curcumin (an inhibitor of nuclear transcription for the inflammatory cascade) abrogated expression of adhesion molecules at a statistically significant level for ICAM-1 in 8/10 PVE, and for E-selectin in all 10 PVE. We conclude that pro-inflammatory agents accumulate in livers during clinical liver transplantation and on rewarming may add to graft injury.