Delayed administration of FK 506 is sufficient to suppress acute rejection changes after aortal transplantation in rats.

Arterial allografts are used now-a-days as a modality in the treatment of vascular prosthesis infections. Prolonged administration of immunosuppressive drugs seemed to be essential for long-time patency rates of alloarterial vascular reconstructions. Nevertheless, the use of immunosuppressives if there exist an acute infection is controversial. The experimental work described herein studied effects of a delayed low-dose FK 506 administration on the development of acute rejection changes 30 days after aortal transplantation in rats. The response of the recipient's immune system to aortal wall antigens of the donor in the field of no immunosuppression resulted in an intimal proliferation and its infiltration by immunocompetent cells of the recipient, necrosis of medial smooth muscle cells, including deposition of immunoglobulins, and a massive adventitial infiltration of CD4 and CD8 positive cells. On the other hand, all the principal histological signs of rejection listed above were suppressed by FK 506 administration, no matter whether the immunosuppressive was administered on day 0 or day 7 after the transplantation.