Ultrastructural study on acute rejection of canine allograft using cyclosporin A.

An electron microscopic study was performed in 7 dogs receiving allotransplantation of the left lung. Three dogs underwent the transplant using the donor's lung which was preserved for 6 hours in cold Collins solution without inflation and flush. Four dogs underwent immediate transplant. Although all of the dogs received orally the same doses of Cyclosporin A (20 mg/kg/day) and Azathioprine (1.5 mg/kg/day) postoperatively, rejection of various stages were found in dogs of two groups. The very early rejection presented the focal mononuclear cell accumulation around blood vessels without the impairment of endothelial and surrounding parenchyma. In the advanced phase of rejection intra- and extravascular mononuclear cell accumulation was present. The mononuclear cells were composed of immunoblastic lymphocytes, plasma cells and alveolar macrophages. The cytoplasm of endothelial cell and basement membrane of blood vessel showed edematous swelling and/or disruption. The intensity of endothelial and subendothelial changes were prominent in small vein and venule. The exudation of much fibrin into the extravascular spaces suggested the progress of fibrotic change and irreversibility of lung damage. There was no clear difference of rejection or impairment of lung parenchyma between a lung preserved 6 hours and a non-preserved lung.