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DNA from rejecting allografts can be detected in recipient nonlymphoid tissues
W L Olszewski1, M Durlik, B Lukomska
1Dept. of Surg. Res. & Transpl., Medical Research Center, Polish Academy of Sciences, Warsaw. wlo@cmdik.pan.pl
Abstract:
The main source of donor DNA in recipients of allograft are "passenger" cells. They are claimed to be responsible for the posttransplantation microchimerism and prolongation of allograft survival. We have noticed that beside of the cellular microchimerism, donor DNA can be found in the recipient tissues at the time of rejection of allograft. In this study we provide evidence for presence in the recipient of both, DNA in "passenger cells" and free DNA in tissues at terminal stage of rejection. Male BN (RTIn) rat heart or skin were transplanted to female LEW (RTII) rats followed by a vascularized bone marrow in hind-limb transplant. CsA was given in a dose of 17mg/kg b.w. for 30 days, then rats were followed until day 100 unless rejection occurred earlier. LEW blood, spleen, mesenteric node and bone marrow cells were stained with moAb OX27 specific for BN but not LEW. Genomic male DNA was isolated and amplified with SRY oligonucleotide. At day 30 and 100 cellular microchimerism was detected in blood, spleen, nodes and bone marrow cells. Donor DNA was detected in recipient skin, liver and heart extracts, beside of lymphoid organs, at the time of rejection of allograft but not when rats were maintained on CsA. Taken together, donor DNA can be detected in recipient tissues at the time of heart or skin rejection. It seems to be released from cells of rejecting grafts and not from "passenger" cells representing only a minor cellular mass compared with the graft.
Insights
Donor DNA is found in recipient tissues during allograft rejection, not just from passenger cells. This free DNA likely originates from the rejecting graft itself, offering new insights into transplant rejection mechanisms.
Area of Science:
- Transplantation immunology
- Molecular biology
- Genetics
Background:
- Passenger cells are considered the primary source of donor DNA in allograft recipients, contributing to microchimerism and prolonged graft survival.
- Previous observations suggest donor DNA presence in recipient tissues beyond cellular microchimerism during allograft rejection.
Purpose of the Study:
- To investigate the presence and origin of donor DNA in recipient tissues during allograft rejection.
- To differentiate between donor DNA from passenger cells and free donor DNA in tissues.
Main Methods:
- Rat models (BN to LEW) for heart and skin allografts with bone marrow transplants.
- Cyclosporine A (CsA) immunosuppression was administered.
- Detection of donor DNA using SRY oligonucleotide amplification in various recipient tissues and cells (blood, spleen, lymph nodes, bone marrow, skin, liver, heart).
- Immunohistochemistry using moAb OX27 to identify donor cells.
Main Results:
- Cellular microchimerism (donor DNA within cells) was detected in blood, spleen, lymph nodes, and bone marrow at 30 and 100 days post-transplant.
- Free donor DNA was identified in recipient skin, liver, and heart tissues during allograft rejection.
- Donor DNA was not detected in tissues when rats were maintained on CsA, indicating immunosuppression prevents its release or detection.
- The presence of free DNA correlated with graft rejection, suggesting release from the rejecting graft.
Conclusions:
- Donor DNA can be detected in recipient tissues during acute heart or skin allograft rejection.
- This free donor DNA appears to originate from the rejecting graft tissue rather than solely from passenger cells.
- The findings challenge the exclusive role of passenger cells in donor DNA presence and suggest a broader mechanism involving graft tissue breakdown during rejection.