Objective: The objective of this study was to examine the feasibility of human interleukin 10 gene transfer into rat lung isografts and to investigate the effect of gene transfer on subsequent ischemia-reperfusion injury. Methods: Male F344 rats were divided into 4 groups and underwent left lung isotransplantation. Twenty-four hours before harvest, 5 x 10E9 pfu (group I, n = 6) or 1 x 10E10 pfu (group II, n = 7) of AdRSVhIL-10 was intravenously administered to donor rats. In group I-C (n = 6) and group II-C (n = 6), serving as controls, 5 x 10E9 pfu and 1 x 10E10 pfu of AdCMVLacZ were administered, respectively. Grafts were preserved for 18 hours at 4°C before implantation and assessed 24 hours after reperfusion. Transgene expression of human interleukin 10 was assessed by both reverse transcriptase-polymerase chain reaction and immunohistochemistry. Graft inducible nitric oxide synthase, tumor necrosis factor α, intercellular adhesion molecule-1, growth-regulated gene product/cytokine-induced neutrophil chemoattractant-1, and monocyte chemotactic protein-1 mRNA expression were assessed by reverse transcriptase-polymerase chain reaction. Isograft gas exchange, exhaled nitric oxide, and myeloperoxidase activity were also analyzed. Results: Dose-dependent transgene expression was detected by reverse transcriptase-polymerase chain reaction and immunohistochemistry. Arterial PO2 in groups I (164.72 ± 85.3 mm Hg) and II (153.19 ± 113 mm Hg) was significantly higher than in groups I-C (82.37 ± 19.1 mm Hg) and II-C (77.95 ± 33.4 mm Hg) (P = .022 and P = .031, respectively). Arterial PCO2 in group I (33.40 ± 6.80 mm Hg) was significantly lower than in group I-C (51.23 ± 11.9 mm Hg) (P = .0096). Myeloperoxidase activity in group II (0.083 ± 0.031 ΔOD · min-1 · mg-1) was significantly lower than in group II-C (0.117 ± 0.028 ΔOD · min-1 · mg-1) (P = .044). The inducible nitric oxide synthase mRNA expression in group II (0.627 ± 0.28) was significantly lower than in group II-C (1.125 ± 0.63) (P = .039). Conclusion: Adenovirus-mediated human interleukin 10 gene transfer in vivo into lung isografts ameliorates subsequent ischemia-reperfusion injury. This results in improved graft gas exchange, reduced neutrophil sequestration, and down-regulation of graft inducible nitric oxide synthase mRNA expression.