Background: After transplantation, donor dendritic cells (DC) migrating to the draining lymph node of the recipient are thought to play an important role in the initiation of graft rejection. In this study, we compared the in vivo migration of DC after allogeneic skin transplantation with that after congeneic skin transplantation.
Methods: A rat model was used with the PVG-RT7b rats as donor animals. These rats have leukocytes bearing an epitope of the leukocyte common antigen that can be recognized by the monoclonal antibody His 41. The cells of the allogeneic (ACI) and congeneic (PVG) recipient animals do not express this marker.
Results: In both recipient rat strains, graft-derived His 41+ DC could be detected in the T cell areas of the draining lymph nodes after skin transplantation. However, the number of migrated His 41+ cells present was lower in the allogeneic recipients. Similar results were obtained when skin DC isolated from the PVG-RT7b rats were injected subcutaneously into the hind footpads of allogeneic and congeneic recipients. Although the numbers of migrated His 41+ DC present were lower, the lymph nodes of the allogeneic recipients were much more enlarged and the grafts were rejected which did not occur in the congeneic recipients.
Conclusions: The presence of donor-derived DC in the graft draining lymph nodes underlines the importance of the direct route of allo-activation. The lower numbers of migrated His 41+ DC in lymph nodes of allogeneic recipients may be the result of killing of the cells after presentation of the allo-antigens to the recipient T cells.