We have recently reported the lack of donor passenger leukocytes in the recipient's lymphoid organs of mice recipient of a skin allograft. On the other hand, we have shown the presence of recipient cells cross-dressed with allogeneic MHC molecules acquired from donor exosomes trafficking from the skin graft to the host lymph nodes. Since lymphatic and blood circulation between the skin graft and the host are reestablished by day 5-7 post-transplantation, it was unclear why passenger leukocytes cannot de found in the host's lymphoid organs.

We hypothesized that early allorecognition caused the deletion of donor cells attempting to leave the graft. To address this question, we investigated the presence of donor passenger leukocytes in untreated wild type mice, wild type mice treated with calcineurin inhibitors (FK506 and CyA) and RAG2 KO mice devoid of adaptive immunity. As seen in table 1, substantial numbers of donor leukocytes were detected in the lymph nodes of recipient mice lacking T cells and mice whose T cell response had been suppressed. These observations build up on the results observed in immunocompetent animals and offer a potential explanation for historical reports of passenger leukocytes in human transplant recipients.

CITATION INFORMATION: Marino J, Gonzalez-Nolasco B, Benichou G. Donor Leukocytes Are Eliminated by the Host's Immune System Shortly After Skin Transplantation in Mice. Am J Transplant. 2017;17 (suppl 3).

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