OBJECTIVE: Systemic injection of donor-derived dendritic cell (DC) progenitors is reported to prolong cardiac allograft survival in nonimmunosuppressed hosts. Our purpose was to identify whether tolerance limited to the cardiac allograft is inducible by direct delivery of DCs to the myocardium, thus diminishing the potential for systemic side effects. METHODS: The donors were 8- to 12-week-old male B10/ H2b mice. The recipients were 8- to 12-week-old male C3H/H2k mice. For DC culture, DCs were propagated from donor bone marrow with granulocytic/macrophage colony stimulating factor (GM-CSF) (GM-CSF DCs) and/or interleukin-4 (IL-4) (GM-CSF+IL-4 DCs). The phenotypes of DCs were analyzed by flow cytometry (FACScan). For DC assay, the JAM test (a DNA fragmentation assay), the mixed lymphocyte reaction (MLR), and flow cytometry were used. For local DC delivery to the myocardium, DCs were injected retrograde into the ascending aorta, and abdominal heterotopic vascularized heart transplantation was performed. Donor heart survival was recorded. RESULTS: JAM assays confirmed the induction of apoptosis in T cells by both DC preparations. Flow cytometry revealed that the GM-CSF DCs expressed diminished co-stimulatory molecules (B7-1 and B7-2) in comparison with the GM-CSF+IL-4 DCs. The mean survival time of cardiac allografts was 13.1 +/- 4.32 days for the controls, 35.0 +/- 25.7 days for DCs cultured with GM-CSF, and 16.9 +/- 7.30 days for DCs cultured with GM-CSF+IL-4. CONCLUSION: Local delivery of GM-CSF DCs may induce graft tolerance and may prove to be more efficient than systemic delivery of DCs. Local delivery of GM-CSF+IL-4 DCs did not prolong cardiac graft survival, suggesting that the immune response elicited may be immunostimulatory.