Transplantation of hematopoietic stem cells for induction of unresponsiveness to organ allografts

Developing immunologic tolerance for transplantation at the fetal stage

Given the shortage of human organs for transplantation, the waiting lists are increasing annually and consequently so is the time and deaths during the wait. As most immune suppression therapy is not antigen specific and the risk of infection tends to increase, scientists are looking for new options for immunosuppression or immunotolerance. Tolerance induction would avoid the complications caused by immunosupressive drugs. As such, taking into account the experience with autoimmune diseases, one strategy could be immune modulation-induced changes in T-cell cytokine secretion or antigen therapy; however, most clinical trials have failed. Gene transfer of MHC genes across species may be used to induce tolerance to xenogenic solid organs. Other options are induction of central tolerance by the establishment of mixed chimerism through hematopoietic stem cell transplantation and the induction of 'operational tolerance' through immunodeviation involving dendritic or Tregs. I propose that, as the recognition and tolerance of proteins takes place in the thymus, this organ should be the main target for immunotolerance research protocols even as early as during the fetal development.

Composite tissue allotransplantation: a review of relevant immunological issues for plastic surgeons

BACKGROUND

Composite tissue allotransplantation of hand, facial and other tissues is now a clinical reality. The terminology, treatment principles, drug combinations, dosage schedules and mechanisms of the immunosuppression medications on which contemporary transplant surgery is based are unfamiliar to plastic surgeons and most healthcare providers outside the field of transplantation medicine. With this in mind, the purpose of this manuscript is to provide plastic surgeons with a comprehensive and understandable review of key immunological principles relevant to composite tissue allotransplantation.

METHODS

We present an overview of the immunological basis of composite tissue allotransplantation aimed at the plastic surgery readership, based on our own experience plus manuscripts sourced from MEDLINE, EMBASE, text books, ancient manuscripts and illustrations.

RESULTS

In this manuscript we provide the reader with a brief history of composite tissue allotransplantation (CTA), a concise description of the immunological terminology, treatment approaches, risks associated with immunosuppressive therapy, risk acceptance, and current research avenues relating to contemporary CTA.

CONCLUSION

Today, as transplant and reconstructive surgeons join forces to move hand and facial tissue allotransplantation into the clinical arena, it is important that plastic surgeons have an understanding of the major immunological principles upon which this new treatment is based.

[Experimental and clinical experience of composite tissues allotransplantation in reconstructive surgery]

Composite tissue allotransplantation (CTA) is a new concept in reconstructive surgery to improve major physical defects with no current solution. Although not a life-saving procedure, tissue replacement by CTA offers great potential for improving quality of life but relies on lifelong immunotherapy. This new practice has become achievable with the refinement of microsurgical techniques, with experience gained from limb and scalp replantations, with the development of organ transplantation and the release of new immunosuppressive drugs. Experimental and clinical research made it possible. The first human cases of CTA proved the reality and the feasibility of the concept. While the early functional results of these allografts are encouraging, they will need to be assessed in the long-term, and development of less toxic - more efficient immonu-suppressive drugs will be a permanent requisite to the broadening of CTA. Although long-term outcome and potential adverse effects of chronic immunosuppression remain uncertain, as for organ transplantation, CTA is already a potential solution for some highly selected patients carrying physical disabilities such as large facial defects and bilateral hand amputation.

First human face allograft: early report

BACKGROUND

Extended soft tissue defects of the face are difficult to reconstruct, and autologous tissue transfers usually lead to poor cosmetic and functional outcomes. We judged that composite tissue transplantation could be valuable in facial reconstructive surgery.

METHODS

We transplanted the central and lower face of a brain-dead woman onto a woman aged 38 years who had suffered amputation of distal nose, both lips, chin, and adjacent parts of the cheeks. Transplantation consisted of revascularisation of right and left facial arteries and veins (ischaemic time 4 h), mucosal repair of oral and nasal vestibules, bilateral anastomoses of infraorbital and mental sensitive nerves, joining of mimic muscles with motor nerve suture on mandibular branch of the left facial nerve, and skin closure. Immunosuppressive treatment was with thymoglobulin, tacrolimus, mycophenolate mofetil, and prednisone. Two infusions of donor bone-marrow cells were given. Follow-up included routine tests, biopsies, physiotherapy, and psychological support.

FINDINGS

The initial postoperative course was uneventful. No surgical complication occurred. Bone-marrow graft and immunosuppression were well tolerated. Mild clinical signs of rejection were seen at day 20. Increased corticoids initially did not reverse rejection, but signs of rejection disappeared after three boluses of prednisone. Anatomical and psychological integration and recovery of sensation were excellent. At the end of the first postoperative week, the patient could eat, and speech improved quickly. Passive transmission of muscle contractions to the graft already exists; physiotherapy is being done to restore dynamic motions around the lips.

INTERPRETATION

The 4-month outcome demonstrates the feasibility of this procedure. The functional result will be assessed in the future, but this graft can already be deemed successful with respect to appearance, sensitivity, and acceptance by the patient.