The effects of early and delayed immunosuppression in experimental tracheal transplantation with omentopexy

Background/Purpose: Best results in experimental tracheal allotransplantati on are obtained when metachronous revascularization by omentopexy and immun osuppression are used. Nevertheless, this method of revascularization impli es in a 4-day period of ischemia to the graft. The aim of this study was to assess the influence of the 4-day period of ischemia on host sensitization as well as the effect of early or delayed immunosuppression on the outcome of the grafts. Methods: Thirty rabbits were submitted to tracheal allotransplantation and divided according to position of the graft (orthotopic or heterotopic trans plants) and the initiation of: immunosuppression (early or delayed). The qu ality of the revascularization was evaluated by the identification of India n ink, perfused through the abdominal aorta, inside the submucosal vessels. The outcome of the grafts was evaluated by histological analysis according to a semiquantitative scale of alterations. Results: Grafts were better revascularized in heterotopic position. Grafts with late immunosuppression presented good outcome only when heterotopicall y positioned. No significant differences were observed in grafts placed het erotopically or orthotopically when immunosuppression was initiated early a fter the transplant. Conclusions: Transient ischemia produced by metachronous revascularization is not the single factor responsible for the histological alterations obser ved in tracheal allografts. These alterations probably also are produced by the activation of immune responses. This activation is more intense in mor e ischemic grafts, but can be suppressed by early administration of immunos uppression. Copyright (C) 1999 by W.B. Saunders Company.