Functional tolerance following face transplantation in the rat.

Abstract

Advances in transplantation immunology and successful transplantation of the human hand and larynx opened the discussion of routine clinical applicability of composite tissue allografts (1–3). The most challenging—and most rewarding—application would be the restoration of facial and scalp deformities by the transplantation of face allografts to patients who are disfigured by cancer, severe burn, and traumatic injuries. Until now, no scientific reports on clinical or experimental face-and-scalp transplantation have been presented. With this communication, we are the first to introduce a feasible and applicable face-and-scalp allograft transplantation procedure across major histocompatability (MHC) barriers, in a rat experimental model. Anatomic studies of facial and scalp harvesting technique (n=15) and pilot isograft transplants (n=14) in Lewis (LEW; RT1l) rats revealed that the composite face-and-scalp graft can be safely transplanted by connecting common carotid arteries and external jugular veins of the donor with external carotid arteries and facial veins of the recipient. Nonvascular isograft control and rejection control experiments (LewisxBrown Norway;LBN[F1];RT1l+n→ LEW) (n=4) were performed to confirm that large skin grafts will not survive without a vascular supply. In these transplants, facial-flap necrosis was evident within 5 to7 days posttransplantation. Next, vascularized isograft (LEW→ LEW;n=4) and allograft transplantations (LBN→ LEW;n=8) across the MHC barrier were performed. At 24 hr posttransplant, 16 mg/kg of cyclosporine A (CsA) was administered daily; and the dose was tapered to 2 mg/kg/day and maintained thereafter at this level. At the present time, isograft controls (survival>190>190 days) and allografts (survival>40>165>200days)(Fig. 1A-C) are under observation, with perfect flap viability and without signs of infection, rejection, or other illness. Figure 1: Functional tolerance in the recipient of a face-and-scalp transplantation across the MHC barrier. At day 182, the face transplant recipient showed no clinical signs of rejection and is in good health (A-C) under low-dose CsA mono-therapy (2 mg/kg/day). Two-color flow cytometry analysis performed on day 120 posttransplant demonstrated RT1n antigen expression of the donor origin on the surface of CD8+ T cell of the recipients (1.2%-dashed circle).(D) At day 120 posttransplant MLR assay revealed the absence of the donor specific tolerance, however confirmed immunocompetence of the face transplant recipient by strong response to the third-party alloantigens in vitro (E).Most of the complications were seen within the first 3 days after transplantation and included food aspiration (two allografts), flap necrosis (two allografts, one isograft), and poor general condition (one allograft). On the fifth day following transplantation, face-transplant recipients resumed their normal routine of eating, drinking, and playing. Vascularized skin allograft used in our face transplant model served as a source of delivery of the donor-specific antigen-presenting cells and stem cells, facilitating skin allograft acceptance in different composite tissue allograft (CTA) models (4). We have shown previously (5) that stable multilineage, donor-specific chimerism correlates with tolerance induction in the CTA model of hind limb allografts where the skin component of the graft was transplanted in the vascularized form. In the current study, flow cytometric assessment of the donor-specific chimerism performed on the 120th day posttransplantation showed 1.2% of CD8+/RT1n+-positive cells in the peripheral blood of the face-transplant recipients (Figure 1D). Because the low level of chimerism may transfer tolerance throughout passenger leukocytes or tolerance-inducing cells, we assume that even a minimal level of the CD8+/RT1n+ double-positive cells found in the peripheral blood leukocytes could facilitate tolerance induction and acceptance of vascularized skin allografts. The ability of the recipient T cells to mount an immune response in the presence of alloantigens under a low level of CsA mono-therapy was determined by mixed lymphocyte reaction (MLR). The allogeneic MLR assay at day 120 after transplantation revealed hyporesponsiveness to the host but increased reactivity to the donor and third-party (ACI;RT1a) alloantigens (Figure 1E). To the best of our knowledge, we are the first to report successful face-and-scalp transplantation in an animal model. In the scope of recent media reports on attempts to perform a face transplant in humans, we believe that our studies will contribute to the understanding of immunological and biological events of this challenging procedure. ACKNOWLEDGMENTS. The authors thank Dr. Robert Fairchild and his laboratory team for their collaborative support. Maria Siemionow Betul Gozel-Ulusal Ali Engin Ulusal Selahattin Ozmen Dariusz Izycki James E. Zins