Development of an ex vivo model of pig kidney perfused with human lymphocytes. Analysis of xenogeneic cellular reactions.

Background: Because of the explosive nature and the extremely rapid process of hyperacute rejection (HAR), significant infiltration of the xenograft by immunocompetent cells is not observed, and the role and the mechanism of action of cell-mediated rejection in discordant xenografts are therefore still under discussion.
Method: We developed an experimental approach using pig kidneys perfused with human peripheral blood lymphocytes (PBL) in which the immunologic barrier of hyperacute rejection was excluded and which mimics the in vivo situation.
Results: PBL retention in the kidney was evaluated at 20-minute intervals for 3 hours. Retention increased from 30% to 80% with the time of perfusion and was specific because significantly fewer syngeneic lymphocytes were retained. Phenotype analysis of recovered PBL showed a significant decrease in natural killer (NK) cells. Immunohistochemical studies revealed the presence of NK cells and T lymphocytes in the glomerular and interstitial tubular structures of the kidney. Functional studies showed a progressive cessation of diuresis and augmentation of renal vascular resistance when the kidney was perfused with PBL. Electron microscopy examinations of kidney sections perfused with PBL showed swollen endothelial zones, suggesting alterations to and damage of the endothelium.
Conclusions: This system provides a valuable model for the study of early discordant xenogeneic cellular rejection and demonstrates the predominance of xenograft infiltration by NK cells.