Acute cellular rejection is relatively common after liver transplantation, typically does not affect graft survival, and is not associated with the development of chronic rejection. Acute cellular rejection is diagnosed when liver enzymes and/or liver function tests are elevated when compared to baseline. The only means of differentiating acute rejection from other liver pathologies is with a liver biopsy. However, even with this invasive diagnostic procedure, it may be difficult to distinguish acute rejection from another disease process, such as injury caused by the hepatitis C virus (HCV) from the native liver. This study will evaluate whether certain patterns of biomarkers in the peripheral blood and/or liver tissue of a liver transplant recipient can be used to determine if the transplanted liver is being rejected by the recipient or sustaining HCV injury. Diagnostic biomarkers that are specific for acute rejection and informative of the severity of HCV recurrence could allow for modulation of immunosuppression therapy and treat the clinical condition without the need for invasive liver biopsies.

Inclusion Criteria:

• Specimens derived from subjects enrolled in the ITN030ST study.
• Availability of adequate biopsy specimens with corresponding blood and/or serum collected within a 10 day window of a for-cause or protocol biopsy.

Exclusion Criteria:

• Withdrawal of consent for the ITN030ST study.
• Absence of consent in the ITN030ST study for the collection and storage of samples of blood and tissue for future research studies.

Patients enrolled in ITN030ST (NCT00135694)