Immunosuppressive effect of irradiation in the murine laryngeal transplantation model: a controlled trial.

Since the first successful human laryngeal transplantation in 1998, research continues toward developing less-morbid immunosuppressive protocols. Although irradiation of donor organs is known to decrease acute rejection, the most advantageous method of radiation delivery is still unknown. Using a rat laryngeal transplant model, we sought to determine the most beneficial timing and delivery method of irradiation. A prospective study was undertaken including 16 treatment arms of 10 to 30 animals each (189 transplantations). The animals received 800 cGy before transplantation to the donor larynx in vivo, the donor larynx in vitro, or the recipient animal's neck. The transplantation occurred at 24 hours, 5 days, or 10 days after irradiation. The transplanted larynges were harvested 15 days after transplantation and histologically scored for rejection. Irradiation of allogeneic transplantations demonstrated a strongly protective effect from rejection as compared to no irradiation (p < .001), regardless of the method of radiation delivery or the amount of time between irradiation and transplantation (p = .78). Irradiation of donor larynges between allogeneic rats has a protective effect, reducing the degree of acute rejection when irradiation is used as the single mode of immunosuppression, and is unrelated to either the timing or the mode of delivery of the irradiation.