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

Best results in experimental tracheal allotransplantation are obtained when metachronous revascularization by omentopexy and immunosuppression are used. Nevertheless, this method of revascularization implies 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.

Thirty rabbits were submitted to tracheal allotransplantation and divided according to position of the graft (orthotopic or heterotopic transplants) and the initiation of immunosuppression (early or delayed). The quality of the revascularization was evaluated by the identification of Indian 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.

Grafts were better revascularized in heterotopic position. Grafts with late immunosuppression presented good outcome only when heterotopically positioned. No significant differences were observed in grafts placed heterotopically or orthotopically when immunosuppression was initiated early after the transplant.

Transient ischemia produced by metachronous revascularization is not the single factor responsible for the histological alterations observed in tracheal allografts. These alterations probably also are produced by the activation of immune responses. This activation is more intense in more ischemic grafts, but can be suppressed by early administration of immunosuppression.