The Positive Effect of Immunosuppression on Adaptation of Venous Allografts to Arterialisation in Rats

Objectives and DesignWe investigated whether immunosuppression was necessary for transplanted allogeneic veins to adapt to arterialisation. We used a transplant rat model with or without immunosuppression.Material and MethodsIliolumbar veins from Lewis (LEW) or Brown–Norway (BN) rats were transplanted into the abdominal aorta of isogeneic (LEW to LEW; group A) or allogeneic (BN to LEW; groups B and C) rats. Group C had daily intramuscular injections of 0.2 mg kg−1 FK506. Light microscope evaluations of grafts were performed at 30 days following transplantation. We determined the presence of endothelial cells, the intensity of intimal proliferation and the degree of infiltration by Lewis major histocompatibility complex (MHC) class II positive, CD4-positive and CD8-positive cells into the adventitia.ResultsGroups A and C displayed similar results in intimal thickness (12.7 ± 7.0 μm vs. 15.0 ± 8.4 μm, respectively) and degree of adventitial infiltration by MHC class II positive (16.6 ± 7.5 vs. 14.6 ± 6.2, respectively), CD8-positive (0.8 ± 1.7 vs. 1.8 ± 2.6, respectively) and CD4-positive (12.5 ± 7.7 vs. 5.8 ± 4.6, respectively) cells. In contrast, allogeneic rats without immunosuppression (group B) showed infiltration of host immunocompetent cells and destruction of the venous wall with no histological signs of arterialisation.ConclusionImmunosuppressive therapy is necessary for venous allograft adaptation to arterialisation in rats.