PhD Scientific Days 2022

Clinical Medicine VIII.

Importance of donor-specific antibodies in the long-term outcome of liver-transplanted children

Text of the abstract

Introduction
Donor-specific antibodies (DSA) develop against human leukocyte antigens (HLA) in the recipient's body. The role of DSA in long-term survivors after liver transplantation has been poorly investigated. Regulatory T cells (Treg) play an important role in the induction and maintenance of immunological tolerance to self and alloantigens.

Aims
Our aim was to examine the association between presence of DSA and condition of liver grafts and to determine the ratio of Foxp3+ Tregs in liver grafts and the association between Tregs and graft fibrosis in liver transplanted children followed up at First Department of Pediatrics, Semmelweis University.

Methods
DSA analysis was performed with Luminex - Single Antigen Bead (SAB) method (147 blood samples from 83 children), median follow up time was 7 years. We analyzed the connection between blood test results (bilirubine, ALP, AST, ALT, GGT, IgG) and the presence of DSA. Graft fibrosis was assessed on protocol liver biopsy samples using Liver Allograft Fibrosis Score (LAFS) and immunostaining for CD4, CD8, Foxp3+ cells and C4d, ultrasound examination and calculated APRI (AST-to-Platelet Ratio Index). Independent two-tailed T test and Welch test were used for statistical analysis.

Results
In cases less than 10 years follow up time, DSA positivity (MFI>500) was 26% (13/50), in other cases, DSA positivity was 52% (17/33). The 83% of total detected DSAs (69/82) belonged to the HLA class II. (64% HLA-DQ, 36% HLA-DR). We analyzed biopsy samples from 18 patients. All of them had fibrosis: mild (LAFS 1-3) N=7, moderate (LAFS 4-5) N=6, severe (LAFS ≥6) N=5. Three of 5 patients with severe fibrosis were DSA positive. Graft inflammation was detected in 86% of DSA positive patients. Immunostaining was performed in biopsy samples of 10 children. In patients with severe fibrosis the mean number of Foxp3 (p=0,11), CD4 (p=0,032) and CD8 (p=0,035) cells/portal tract were higher than in mild and moderate fibrosis (N=6). We did not detect association between laboratory blood test results or APRI and the presence of DSA.

Conclusion
We found that graft inflammation is more frequent in the DSA positive patients, which could develop to fibrosis during years. The ratio of DSA positive liver transplanted patients was higher after 10 years follow-up time.

Funding
The work funded by PhD research budget.