Suppressive and antigen experienced Treg abundance may determine drug withdrawal in autoimmune hepatitis 4685

Abstract Description Aim To characterize Treg subpopulations from children with: post-transplant alloimmune hepatitis (DAIH), biopsy proven acute rejection (AR), normal liver graft function (LTC), & non-transplanted children with autoimmune hepatitis (AIH). Methods Intrahepatic lymphocytes & PBMC were enriched for CD4 & separately expanded under Treg polarizing conditions for 14-days. Expanded cells were stained with metal-tagged antibodies & acquired on CyTOF mass cytometer. Methylation status of 11 cytosine guanine dinucleotide sites within the FOXP3 Treg-specific demethylated region (TSDR) assessed by targeted NextGen Bisulfite Sequencing of DNA. Result 29 children (11 AR, 7 AIH, 7 LTC, & 3 DAIH). 3 Treg subpopulations with distinct phenotypes identified: Treg A with a high frequency of CD73+, CD39+, Nrp1+ within Foxp3hi CD127lo Tregs. Treg B with abundance of HLA-DR, CD95 within CD45RA+resting/naïve Tregs. Treg C with abundance of HLA-DR, CD73 within CCR4+ effector Tregs. All 3 subpopulations predominate in children with AIH (p < 0.05). Expanded Tregs demonstrated >90% FOXP3+expression. FOXP3 TSDR cytosine guanine dinucleotide sites in Tregs ranged between 64% - 99% unmethylated. Treg A & Treg C were positively correlated with one another (r = 0.94; p = 3.51E-11), & negatively correlated with serum amino transferase level (Treg A: r= -0.58; p = 0.004. Treg C: r= -0.49; p = 0.017). Conclusion Suppressive and antigen experienced Treg abundance may determine drug withdrawal in AIH. Funding Sources None Topic Categories Transplantation Immunology (TRAN)