Donor dendritic cell persistence in organ allograft recipients in the absence of immunosuppression.

Donor-derived leukocytes are known to persist in the peripheral blood of organ allograft recipients after withdrawal of all immunosuppressive drug therapy and can exert a donor-specific veto effect. Antigen-presenting cells (APC), in particular dendritic cells (DC), have been proposed as a candidate for this veto leukocyte. Myeloid DC were derived from the peripheral blood of two ion-compliant organ transplant recipients: D. S., a heart transplant recipient, and J. M., a liver transplant recipient. Donor-specific signal was enriched in the cultured DC fraction relative to whole blood for both patients. The clinical outcome in each patient was different: D. S. lost his heart allograft due to biopsy-proven acute and chronic rejection 2.5 years after discontinuing anti-rejection medication; J. M. continues to maintain adequate liver function. The results have important implications for the planned withdrawal of immunosuppression in tolerance protocols as DC may play a role either in the maintenance of tolerance or immune activation.