T-reg mediated suppression of the allograft response in the draining lymph node.

We previously demonstrated that T-regs inhibit proliferation of graft-reactive T cells in the draining lymph node (DLN), suggesting that this site may be important for regulation. TCR transgenic mice (TS1) specific for viral hemagglutinin (HA) provided antigen-specific T cells for adoptive transfer into syngeneic Balb/c hosts bearing HA+ skin grafts. T-regs were obtained from (TSlxHA28)Fl mice known to have an expanded population of HA-specific T-regs. To determine whether the lymph node is an independent site of suppression, we developed a model in which donor antigen that migrates from the allograft to the DLN drives T-cell activation after graft removal. T-regs that did not encounter the allograft itself remained able to inhibit graft antigen-specific T-cell proliferation in the DLN. Alloantigen-induced regulation can occur in the absence of the graft. This finding identifies the DLN as a potentially critical site of regulation in the early posttransplant period.