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 non‐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. J. Leukoc. Biol. 66: 301–305; 1999.