Regulatory T cells (Tregs) are instrumental in the induction and maintenance of tolerance, including in transplantation. Tregs induce allotolerance by interacting with antigen-presenting cells (APC) and T cells, interactions that require their proper homing to the lymphoid tissues. Using a well characterized model of corneal allotransplantation, we demonstrate here that Tregs in the draining LN of allograft acceptors, but not rejectors, colocalize with APC in the paracortical areas and express high levels of C-C motif chemokine receptor 7 (CCR7). In addition, we show that Treg expression of CCR7 is important not only for Treg homing to the draining LN, but also for optimal Treg suppressive function. Finally, we show that Tregs augmented for CCR7 expression by their ex vivo stimulation with the CCR7-ligand CCL21 show enhanced homing to the draining LN of allograft recipients and promote transplant survival. Together, these findings suggest that CCR7 expression is critical for Treg function and migration, and that conditioning of Treg for maximal CCR7 expression may be a viable strategy for promoting allograft survival
