Forkhead box P3 (FOXP3) mRNA expression immediately after living-donor liver transplant.

The forkhead box P3 (FOXP3) gene is considered to be the master gene of regulatory T cells. The significance of regulatory T cells in liver transplant has been investigated in previous reports, but quantitative FOXP3 messenger RNA (mRNA) expression after living-donor liver transplant has not been assessed. The objective of this study was to determine whether the human FOXP3 gene is a good marker for regulatory activity in T cells in living-donor liver transplant recipients during the immediate posttransplant period. In peripheral blood mononuclear cells of 15 living-donor liver transplant recipients during the first month after transplant; we measured the population of CD4+CD25+ T cells using flow-assisted cell sorting and the expression of FOXP3 mRNA using real-time polymerase chain reaction. Fold induction of FOXP3 mRNA significantly increased on postoperative day 7 (3.3-fold) compared with the reference preoperative value (P < .01) but returned to baseline by 28 days after transplant. The population of CD4+CD25+ T cells did not change significantly. Expression of FOXP3 mRNA on days 14, 21, and 28 were lower in recipients with acute cellular rejection within 60 days after living-donor liver transplant. Increased expression of FOXP3 mRNA immediately after living-donor liver transplant might be influenced by activation of T cells including regulatory T cells and other T cells. However, after stabilization of these activation profiles, it seems likely that FOXP3mRNA expression is associated with graft acceptance. Further studies are necessary with measurement of FOXP3 mRNA expression at appropriate sampling points.