Short-course immunosuppression after tracheal allotransplantation in dogs.

It is desirable to minimize immunosuppression after allotransplantation. We examined the usefulness of a short course of immunosuppression after tracheal allotransplantation in 35 dogs. Five animals with six-ring tracheal autografts served as controls (group I, n = 5). Thirty animals with six-ring tracheal allografts were randomly classified into five groups as follows: no immunosuppression (group II, n = 6), azathioprine for only 1 postoperative week (group III, n = 7), azathioprine for 2 postoperative weeks (group IV, n = 7), azathioprine for 3 postoperative weeks (group V, n = 5), and mizoribine for 3 postoperative weeks (group VI, n = 5). All allografts in groups II through VI sustained rejection, but there was no difference in mononuclear cell infiltration of the grafts among the groups. The only grafts with long-term viability were those in groups I and VI, as demonstrated by graft patency and epithelialization. We conclude that immunosuppression with mizoribine for only a short course after transplantation may allow long-term viability of tracheal allografts.