*Purpose: In January 2021, we performed the first single stage vascularized tracheal transplantation for reconstruction of a 9.5 cm tracheal airway defect. One year after transplantation, we report on the patient’s progress.

*Methods: Following a 9.5 cm vascularized tracheal transplantation, we have regularlymonitored the patient with endoscopy, tracheal biopsies, dye motility studies, and donor-derived cell free DNA testing.

*Results: While the allograft initially lost ciliated epithelium, within 30 days after transplantation, the graft was repopulated with functional ciliated epithelium based on histology and dye motility studies. Our analysis of the human tracheal transplant mucosa has shown a progressive re-epithelialization with recipient-derived epithelium (79.8% recipient- derived cells at 90 days post- transplant), followed by a re- population of the allograft with donor- derived epithelium. In an interesting reversal, the initial allograft chimera comprised of predominantly recipient derived epithelium, has become dominated with donor – derived epithelium (>94%). Based on biopsy, free cell DNA, and endoscopic examination, we have seen no evidence of acute or chronic rejection in the human tracheal allograft.

*Conclusions: In spite of data demonstrating that vascular composite allografts (VCA), such as hand and face transplantation, experience a high rate (~80%) of acute rejection and a 50% rate of chronic rejection, six- fold higher than solid organ transplantation, we have seen no evidence of acute or chronic rejection in the human tracheal allograft. The dynamics of re- epithelialization of the allograft and development of an immunological chimera may provide an opportunity to consider de- escalation of immunosuppression.

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