Hepatic Infiltrates in Operational Tolerant Patients After Liver Transplantation Show Enrichment of Regulatory T Cells Before Proinflammatory Genes Are Downregulated.

Immunosuppression can be discontinued from selected and stable patients after liver transplantation resulting in spontaneous operational tolerance (SOT), although the underlying mechanisms remain elusive. Thus, we analyzed serial liver biopsy specimens from adult liver recipients enrolled in a prospective multicenter immunosuppression withdrawal trial that used immunophenotyping and transcriptional profiling. Liver specimens were collected before the initiation of weaning, at the time of rejection, or at 1 and 3 years after complete drug discontinuation. Unexpectedly, the tolerated grafts developed portal tract expansion with increased T cell infiltration after immunosuppression withdrawal. This was associated with transient and preferential accumulation of CD4(+) FOXP3(+) cells and a trend toward upregulation of immune activation and regulatory genes, without signs of rejection. At the same time, no markers of endothelial damage or activation were noted. Portal infiltrates persisted at 3 years but were characterized by decreased expression of genes associated with chronic immunological damage. Further, SOT was not associated with a progressive liver fibrosis up to 5 years. These data suggest that SOT involves several mechanisms: a long-lasting local immune cell persistence with a transient regulatory T cells accumulation followed by a downregulation of immune-activated genes over years. These results have important implications for designs and follow-up of weaning trials.

Molecular Characterization of Acute Cellular Rejection Occurring During Intentional Immunosuppression Withdrawal in Liver Transplantation.

Acute cellular rejection occurs frequently during the first few weeks following liver transplantation. During this period, its molecular phenotype is confounded by peri- and postoperative proinflammatory events. To unambiguously define the molecular profile associated with rejection, we collected sequential biological specimens from 55 patients at least 3 years after liver transplantation who developed rejection during trials of intentional immunosuppression withdrawal. We analyzed liver tissue and blood samples obtained before initiation of drug withdrawal and at rejection, alongside blood samples collected during the weaning process. Gene expression profiling was conducted using whole-genome microarrays and real-time polymerase chain reaction. Rejection resulted in distinct blood and liver tissue transcriptional changes in patients who were either positive or negative for hepatitis C virus (HCV). Gene expression changes were mostly independent from pharmacological immunosuppression, and their magnitude correlated with severity of histological damage. Differential expression of a subset of genes overlapped across all conditions. These were used to define a blood predictive model that accurately identified rejection in HCV-negative, but not HCV-positive, patients. Changes were detectable 1-2 mo before rejection was diagnosed. Our results provide insight into the molecular processes underlying acute cellular rejection in liver transplantation and help clarify the potential utility and limitations of transcriptional biomarkers in this setting.