Monitoring of CD4CD25highIL-7Rhigh activated T Cells in Kidney Transplant Recipients

Background and objectives In humans, circulating CD4CD25high T cells contain mainly regulatory T cells (Treg; FoxP3IL-7Rlow), but a small subset is represented by activated effector T cells (Tact; FoxP3IL-7Rhigh). The balance between Tact and Treg may be important after transplantation. The aim of this study was first to analyze and correlate CD4CD25high Tact and Treg with the clinical status of kidney transplant recipients and second to study prospectively the effect of two immunosuppressive regimens on Tact/Treg during the first year after transplantation. Design, setting, participants, & measurements CD4CD25high Tact and Treg were analyzed by flow cytom-etry, either retrospectively in 90 patients greater than 1 year after kidney transplantation (cross-sectional analysis) or prospectively in 35 patients receiving two immunosuppressive regimens after kidney transplan-tation (prospective analysis). Results A higher proportion of Tact and a lower proportion of Treg were found in the majority of kidney recipients. In chronic humoral rejection, a strikingly higher proportion of Tact was present. A subgroup of stable recipients receiving calcineurin inhibitor–free immunosuppression (mycophenolate mofetil, azathio-prine, or sirolimus) had Tact values that were similar to healthy individuals. In the prospective analysis, the proportion of Tact significantly increased in both immunosuppression groups during the first year after transplantation. Conclusions These data highlight distinct patterns in the proportion of circulating Tact depending on the clinical status of kidney recipients. Moreover, the prospective analysis demonstrated an increase in the pro-portion of Tact, regardless of the immunosuppressive regimen. The measurement of Tact, in addition to Treg, may become a useful immune monitoring tool after kidney transplantation