DETECTION OF CANINE ALLOGRAFT LUNG REJECTION BY PULMONARY LYMPHOSCINTIGRAPHY

We previously demonstrated that lymphoscintigraphy could be used to st udy pulmonary lymphatic flow. Radiocolloids, high-molecular-weight pro teins tagged with radioactive markers, are injected percutaneously in the periphery of the lung. These molecules enter the lymph, are transp orted via lymphatic channels, and concentrate in the tributary hilar a nd mediastinal lymph nodes, where they can be visualized by nuclear sc an. The goal of this study was to determine whether pulmonary lymphosc intigraphy could be used to detect allograft rejection after lung tran splantation. Thirteen mongrel dogs underwent left lung allotransplanta tion. Cyclosporine 15 mg/kg per day and azathioprine 1 mg/kg per day w ere given orally for postoperative immunosuppression. Lymphoscintigrap hic studies were obtained 1 week after the operation and then at weekl y intervals. In five dogs (group A), immunosuppression was continued u ntil the animal died or was put to death 6 weeks later. Lymphoscintigr aphy demonstrated reestablishment of lymphatic drainage between the lu ng graft and the mediastinum in all the animals 2 to 4 weeks after tra nsplantation. In eight dogs (group B), immuno-suppression was disconti nued after reestablishment of graft lymphatic drainage was documented by two consecutive lymphoscintigraphic studies. The dogs continued to be studied with weekly scans. In group B, lymphatic drainage from the lung graft to the mediastinum disappeared 1 to 4 weeks after immunosup pression was stopped, Rejection was diagnosed clinically and confirmed histologically with open lung biopsies and/or autopsies in all animal s. This study shows that canine allograft lung rejection is associated with disappearance of lymphatic drainage from lung graft to mediastin um, which can be documented by pulmonary lymphoscintigraphy, a minimal ly invasive technique that can be easily repeated. Pulmonary lymphosci ntigraphy may be useful for early detection of lung allograft rejectio n.