Donor DNA is detected in recipient blood for years after kidney transplantation using sensitive forensic medicine methods.

Background: Transplanted vascularized organs shed passenger cells, normal constituents of whole organs, that migrate to recipient lymphoid tissues and produce microchimerism. These cells lyzed by recipient cytotoxic cells release cellular organelles into the recipient circulation. In addition, warm and cold ischemia as well as immune rejection of the transplanted organ or tissue bring about destructive changes in the graft parenchymatous cells. The knowledge of the fate of donor DNA distributed in passenger cells and in fragments of disrupted nuclei as well as the role of recipient cells internalizing donor DNA could give some insight into the mechanism of graft destruction and immunization or tolerance to donor antigens.

Material/methods: In this study we provide evidence that forensic medicine testing of polymorphic genes for phospholipase A2, cytochrome P450 and locus D1S80 may be useful for the detection of donor DNA microchimerism in kidney transplant recipients in sex-matched combinations as well as previous blood transfusion recipients.

Results: Donor DNA was detected in recipient whole blood even 2 years after kidney transplantation.

Conclusions: The biological significance of our findings is not clear. We speculate that donor DNA fragments in recipient immune cells may play a role in the immunization/tolerance process to allogeneic antigens.