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Repopulation of donor heart with recipient bone marrow-derived dendritic cells does not prevent acute rejection
Repopulation of Donor Heart With Recipient Bone Marrow-Derived Dendritic Cells Does Not Prevent Acute Rejection M. Maksymowicz, W.L. Olszewski, and E. Cybulska
A
LLOGRAFT passenger dendritic cells (DC) and intravascular lymphocytes leave the transplanted organ after grafting and migrate to recipient lymphoid tissues. The graft DC belong to the group of professional antigen presenting cells (APC) evoking a “direct” allogeneic response by the recipient. They may play opposing roles in peripheral tolerance and allograft rejection.1 The tolerogenic versus immunogenic effects of the microchimerism related to DC depends on the host’s immunological maturity and the antigenic disparities.2 In man rejection of solid organ grafts rather than tolerance is generally observed. Tolerance may be limited to the chimeric cells but not to graft antigens that are not expressed on the chimeric cells protect the graft against responses to antigens that are not expressed by the chimeric cells.2 Creating chimeric organs with recipient-type DC would eliminate the effect of donor passenger cells on the rejection process (direct pathway) and expose the role of graft antigens via the indirect allogenic response. The question arises as to whether the chimeric organ deprived its own DC and repopulated by recipient DC elicits a weaker recipient reaction thereby resulting in prolonged graft survival. A vascularized bone marrow transplant (VBMTx) from the prospective recipient to the lethally irradiated heart donor, functioning for a period of 14 days, was used to fully replace donor DC with recipient DC.
MATERIALS AND METHODS LEW rats were irradiated with 8 Gy and 24 hours later received a BN rat vascularized hind-limb graft (HLTx) as a source of bone marrow (BM)-derived DC. Fourteen days later hearts (H) from chimeric LEW rats bearing BN HLtx were transplanted into untreated BN hosts. For controls, H from irradiated and untreated LEW rats were grafted into normal BN rats. To check for depletion of DC from LEW H staining with OX6 (anti-class II) was used and to prove repopulation with BN DC, OX27 moAb specific for BN but not LEW rats were also used. In MLR, responsiveness of naive BN recipient lymphocytes was examined after stimulation by LEW (BN DC repopulated donor) cells as well as of BN splenocytes obtained on the fifth day after LEW H(BN DC) transplantation with naive LEW splenocytes. © 2002 by Elsevier Science Inc. 655 Avenue of the Americas, New York, NY 10010 Transplantation Proceedings, 34, 683–684 (2002)
RESULTS
LEW H became depopulated of their own DC by 3 days after irradiation and were fully repopulated by BN DC within 14 days after irradiation. The DC-depopulated LEW Hs transplanted to naive BN were rejected within 7 ⫾ 2 days. The BN DC-repopulated LEW Hs were rejected by naive BN within 72 days. Repopulation of LEW Hs by BN DC was followed by strong expression of class II antigens on endothelial cells of the prospective graft. Moreover, accumulation of BN-type mononuclear cells could be seen in larger vessels. In MLR, LEW splenocytes from rats with a 14-day VBMTx were found to be very weak stimulators of naive BN cells. BN splenocytes harvested on the fifth day after transplantation of LEW H repopulated with BN DC, responded strongly to naive LEW splenocytes. DISCUSSION
This study provided the following observations: (a) lack of prolongation of survival time of heart allografts deprived of its own dendritic cells and repopulate with recipient-type dendritic cells, (b) stimulation of allogeneic reactions in irradiated donor hearts by chimeric recipient-type bone marrow-derived dendritic cells during the repopulation process, (c) low stimulatory activity of splenocytes from the irradiated donor repopulated with recipient-type bone marrow cells to naive recipient splenocytes. The graft resident dendritic cells are potent antigen presenting cells and initiate the “direct” allogenic reaction pathway. They are responsible for a vigorous rejection process of the allograft.3 In our donor-recipient strain combination depletion of donor APC did not mitigate the rejection process. Other authors have also reported that deprivation of the allograft of passenger cells by irradiation prior to transplantation did not prolong the graft survival time and even prevented graft From the Department of Surgical Research and Transplantology, Medical Research Center, Polish Academy of Sciences, Warsaw, Poland and The Norwegian Radium Hospital, Oslo, Norway. Address reprint requests to M. Maksymowicz, Department of Surgical Research and Transplantology, Medical Research Center, Polish Academy of Sciences, 02 106 Warsaw, Pawinski Street 5, Poland. 0041-1345/0⫺2000/$–see front matter PII S0041-1345(01)02886-X 683
684
acceptance.4 Replacement of graft dendritic cells with recipient cells was ineffective to prolong allograft survival in our study akin to the results reported by Krasinskas et al in a high-responder rat strain combination.5 In their study donor hearts were repopulated with recipient cells using one bolus of bone marrow cell infusion. Our model of repopulation was different as recipient bone marrow cells were seeded into the prospective heart donor for 14 days. This period was long enough for the recipient cells populating the donor heart to initiate an allogenic reaction while still in the donor’s body. This may explain why the rejection reaction occurred so rapidly after transplantation to the naive recipient. A low level of response of recipient cells in MLR to splenocytes from a donor
MAKSYMOWICZ, OLSZEWSKI, AND CYBULSKA
replaced with recipient bone marrow could be explained by a lack of donor APC in the stimulating population. To sum up, replacement of a donor heart with recipient APC does not result in prolongation of graft survival but rather it initiates a rejection reaction in the donor. REFERENCES 1. Fairchild PJ, Waldmann H: Curr Opin Immunol 12:528, 2000 2. Anderson CC, Matzinger P: Nature Med 7:80, 2001 3. Lindahl KF, Wilson DB: J Exp Med 145:508, 1977 4. Sun J, McCaughan GW, Gallghager ND, et al: Transplantation 60:233, 1995 5. Krasinskas AM, Eiref SD, MacLean AD, et al: Transplantation 70:514, 2000
A
LLOGRAFT passenger dendritic cells (DC) and intravascular lymphocytes leave the transplanted organ after grafting and migrate to recipient lymphoid tissues. The graft DC belong to the group of professional antigen presenting cells (APC) evoking a “direct” allogeneic response by the recipient. They may play opposing roles in peripheral tolerance and allograft rejection.1 The tolerogenic versus immunogenic effects of the microchimerism related to DC depends on the host’s immunological maturity and the antigenic disparities.2 In man rejection of solid organ grafts rather than tolerance is generally observed. Tolerance may be limited to the chimeric cells but not to graft antigens that are not expressed on the chimeric cells protect the graft against responses to antigens that are not expressed by the chimeric cells.2 Creating chimeric organs with recipient-type DC would eliminate the effect of donor passenger cells on the rejection process (direct pathway) and expose the role of graft antigens via the indirect allogenic response. The question arises as to whether the chimeric organ deprived its own DC and repopulated by recipient DC elicits a weaker recipient reaction thereby resulting in prolonged graft survival. A vascularized bone marrow transplant (VBMTx) from the prospective recipient to the lethally irradiated heart donor, functioning for a period of 14 days, was used to fully replace donor DC with recipient DC.
MATERIALS AND METHODS LEW rats were irradiated with 8 Gy and 24 hours later received a BN rat vascularized hind-limb graft (HLTx) as a source of bone marrow (BM)-derived DC. Fourteen days later hearts (H) from chimeric LEW rats bearing BN HLtx were transplanted into untreated BN hosts. For controls, H from irradiated and untreated LEW rats were grafted into normal BN rats. To check for depletion of DC from LEW H staining with OX6 (anti-class II) was used and to prove repopulation with BN DC, OX27 moAb specific for BN but not LEW rats were also used. In MLR, responsiveness of naive BN recipient lymphocytes was examined after stimulation by LEW (BN DC repopulated donor) cells as well as of BN splenocytes obtained on the fifth day after LEW H(BN DC) transplantation with naive LEW splenocytes. © 2002 by Elsevier Science Inc. 655 Avenue of the Americas, New York, NY 10010 Transplantation Proceedings, 34, 683–684 (2002)
RESULTS
LEW H became depopulated of their own DC by 3 days after irradiation and were fully repopulated by BN DC within 14 days after irradiation. The DC-depopulated LEW Hs transplanted to naive BN were rejected within 7 ⫾ 2 days. The BN DC-repopulated LEW Hs were rejected by naive BN within 72 days. Repopulation of LEW Hs by BN DC was followed by strong expression of class II antigens on endothelial cells of the prospective graft. Moreover, accumulation of BN-type mononuclear cells could be seen in larger vessels. In MLR, LEW splenocytes from rats with a 14-day VBMTx were found to be very weak stimulators of naive BN cells. BN splenocytes harvested on the fifth day after transplantation of LEW H repopulated with BN DC, responded strongly to naive LEW splenocytes. DISCUSSION
This study provided the following observations: (a) lack of prolongation of survival time of heart allografts deprived of its own dendritic cells and repopulate with recipient-type dendritic cells, (b) stimulation of allogeneic reactions in irradiated donor hearts by chimeric recipient-type bone marrow-derived dendritic cells during the repopulation process, (c) low stimulatory activity of splenocytes from the irradiated donor repopulated with recipient-type bone marrow cells to naive recipient splenocytes. The graft resident dendritic cells are potent antigen presenting cells and initiate the “direct” allogenic reaction pathway. They are responsible for a vigorous rejection process of the allograft.3 In our donor-recipient strain combination depletion of donor APC did not mitigate the rejection process. Other authors have also reported that deprivation of the allograft of passenger cells by irradiation prior to transplantation did not prolong the graft survival time and even prevented graft From the Department of Surgical Research and Transplantology, Medical Research Center, Polish Academy of Sciences, Warsaw, Poland and The Norwegian Radium Hospital, Oslo, Norway. Address reprint requests to M. Maksymowicz, Department of Surgical Research and Transplantology, Medical Research Center, Polish Academy of Sciences, 02 106 Warsaw, Pawinski Street 5, Poland. 0041-1345/0⫺2000/$–see front matter PII S0041-1345(01)02886-X 683
684
acceptance.4 Replacement of graft dendritic cells with recipient cells was ineffective to prolong allograft survival in our study akin to the results reported by Krasinskas et al in a high-responder rat strain combination.5 In their study donor hearts were repopulated with recipient cells using one bolus of bone marrow cell infusion. Our model of repopulation was different as recipient bone marrow cells were seeded into the prospective heart donor for 14 days. This period was long enough for the recipient cells populating the donor heart to initiate an allogenic reaction while still in the donor’s body. This may explain why the rejection reaction occurred so rapidly after transplantation to the naive recipient. A low level of response of recipient cells in MLR to splenocytes from a donor
MAKSYMOWICZ, OLSZEWSKI, AND CYBULSKA
replaced with recipient bone marrow could be explained by a lack of donor APC in the stimulating population. To sum up, replacement of a donor heart with recipient APC does not result in prolongation of graft survival but rather it initiates a rejection reaction in the donor. REFERENCES 1. Fairchild PJ, Waldmann H: Curr Opin Immunol 12:528, 2000 2. Anderson CC, Matzinger P: Nature Med 7:80, 2001 3. Lindahl KF, Wilson DB: J Exp Med 145:508, 1977 4. Sun J, McCaughan GW, Gallghager ND, et al: Transplantation 60:233, 1995 5. Krasinskas AM, Eiref SD, MacLean AD, et al: Transplantation 70:514, 2000