Histologic and hemodynamic investigation on canine lung allografts.

Histologic and hemodynamic investigations were performed on 26 mongrel dogs that underwent left lung allotransplantation. All dogs received cyclosporin A and azathioprine as immunosuppressants and were divided into two groups. In the 10 Group I dogs, no preservation was performed and the animals were followed until death. The 16 Group II dogs were subdivided into two groups; Group II-A dogs received the transplantation after 6 hours preservation and Group II-B dogs received it after no preservation. All dogs in Group II were sacrificed within 14 days following the transplantation. Seven of the dogs in Group I survived for over 90 days. The major histologic findings of Group I were pneumonitis, fibrotic interstitial changes and pleural thickening. Atypical pneumocytes were observed in three dogs, however structural changes of the bronchioles, suggesting obliterative bronchiolitis, were obscure. In Group II, 75 per cent of the dogs demonstrated the histologic features of rejection and early rejection was seen in a few dogs. Under electron microscopy, vascular wall damage was indicated by swollen endothelial cytoplasm and disrupted basement membranes. Small lymphocytes accumulating around the vessels showed lymphoblastic figures with rich intracytoplasmic organellae. The mean pulmonary arterial pressure measured by right pulmonary artery (PA) occlusion was elevated just after the transplantation in Group II, but decreased on the 7th day. The mean PA was again elevated on the 14th day in those dogs in which diffuse mononuclear cell cuffing was demonstrated. We consider that the PA-occlusion test can be used for determining the degree of rejection.