Background: Kinetics and role of host and donor dendritic cells (DCs) in transplantation immunity are still ill-defined. Using a rat cardiac transplantation model, we studied DC trafficking and sites for allosensitization.
Methods: Host and donor DCs were defined as host- or donor-type class II major histocompatibility complex antigen single-positive cells by double-immunostaining. Proliferative response of both donor and host cells were also analyzed.
Results: Host DCs were recruited to the graft soon after transplantation. These cells represented definitive precursors because of high labeling index by a continuous bromodeoxyuridine infusion, their small round shape, and their putative bone marrow origin. Donor interstitial DCs showed a significant self-replicating capability. Both recruited host DCs in a regraft experiment and donor DCs preferentially performed blood-borne migration to the T-cell area of host spleen. Furthermore, they also migrated to the T-cell area of hepatic lymph nodes after executing the sinusoids-lymph translocation as a novel pathway for these DCs. Selectively at their migration sites, a strong T-cell proliferative response occurred, which preceded that in the graft tissues. Removal of spleen and hepatic lymph nodes significantly prolonged the mean graft survival time.
Conclusion: We conclude that allogeneic heart transplantation induces the recruitment of host DC precursors to the graft tissues and the blood-borne migration of both recruited host and donor DCs to the host spleen and hepatic nodes where effector cells are predominantly sensitized.