This is a retrospective observational study in liver transplantation recipients with or without allograft liver fibrosis. Based on the GM-seq and Tcr-Seq data, a novel diagnostic model including DNA-methylation and TCR-Seq biomarkers will be established.

This is a retrospective study on 60 patients who had previously received liver transplantation in our hospital. The patients will be stratified according to age, including 20 children and 20 adults with allograft liver fibrosis after liver transplantation, while 10 children and 10 adults with fibrosis, respectively.

1. The differential analysis of DNA-methylation will be performed between the allograft liver fibrosis cohort and the control cohort based on the GM-seq sequencing data. And the fibrosis-specific DNA-methylation CpG sites or regions in liver and peripheral blood will be explored in the liver transplantation recipients.
2. The abundance and diversity of TCR between the allograft liver fibrosis cohort and the control cohort will be analyzed. And the fibrosis-specific TCR sequence of allograft liver fibrosis will be screened based on TCR-Seq sequencing and tNGS.
3. The characteristics of DNA-methylation and TCR-Seq biomarkers in allograft liver fibrosis population will be defined. And the similarities and differences of the characteristics between children and adults will be explored.
4. Based on the GM-seq and Tcr-Seq data, a novel diagnostic model including DNA-methylation and TCR-Seq biomarkers will be established.

Inclusion Criteria:

1. Living donor liver transplantation of left outer lobe or left half liver for biliary atresia in children (≤18 years old), or orthotopic liver transplantation for hepatitis B cirrhosis in adults (> 18 years old), regardless of gender;
2. Oral tacrolimus immunosuppressive therapy;
3. Received liver transplantation in our hospital for the first time and did not receive liver transplantation again;
4. Patients need to be admitted to hospital for programmed liver biopsy or receive liver biopsy due to abnormal liver function;
5. Complete clinical data and samples (including liver puncture biopsy specimens, plasma, and PBMC of the same period);
6. The subjects or their guardians voluntarily join the study, sign the informed consent, comply well, and cooperate with follow-up.

Exclusion Criteria:

1. Combined multi-organ transplantation;
2. Pregnancy or lactation;
3. Severe systemic infection;
4. Contraindications of liver biopsy with multiple organ failure or coagulation dysfunction;
5. Previous history of allergy to narcotic or sedative drugs;
6. In the stage of acute rejection hormone shock therapy;
7. Incomplete clinical data and samples;
8. Situations considered unsuitable for inclusion by other researchers.

Adult or pediatric recipients who underwent liver transplantation