EXPERIMENTAL PIGLET LUNG TRANSPLANTATION - HISTOLOGICAL BIOPTIC CHANGES AND AUTOPSY FINDINGS

To investigate difficulties in diagnosing pulmonary rejection and to c reate a new model to observe long-term histological consequences, 21 p iglets were subjected to left single lung transplantation. Five of the se transplants served as targets for unmodified rejection in piglets w ithout immunosuppression (Group I), 13 recipients were treated with cy closporin A, azathioprine and methylprednisolone (Group II), and in 3 cases reimplantation of an autograft was performed (Group III). In the course of postoperative graft monitoring, transthoracic/bronchial bio psies were obtained on days 3, 5, 7, 10, 14, and 20, and thereafter le ss frequently up to 134 days. In the unmodified rejection group, graft s consolidated in one week and histologically presented perivascular m ononuclear cell infiltrates, except for one case which showed vasculit is. Lymphocytic bronchiolitis and or peribronchiolar infiltrate was pr esent in three of the four autopsied grafts. In Group II acute rejecti on was detected six times in three piglets, and all except one of thes e specimens had a peribronchiolar component. Although no incontestable bronchiolitis obliterans developed, mild to moderate chronic oblitera tive vascular lesions were detected in all immunosuppressed piglets (n =3) surviving more than 80 days. Contralateral lungs and Group III aut ografts showed mild changes related to the operation itself and inters titial swine endemic pneumonia (SEP). Chronic changes related to rejec tion were limited to the vascular wall. The mainly inflammatory bronch iolar changes are thought to present an incipient phase leading to obl iterative lesions.