Recipient Kupffer cell influx into xenografted liver.

Previously we reported that the combination of total lymphoid irradiation (TLI), cyclosporine A (CsA), and splenectomy have an immunosuppressive effect sufficient to significantly prolong liver xenograft survival in the LVG hamster to the LEW rat model. Using this model, we have investigated recipient Kupffer cell influx into the xenografted liver. In the rat liver, the Kupffer cells are heavily stained with Ki-M2R, a rat anti-macrophage monoclonal antibody, whereas sinus endothelial cells and liver parenchymal cells are invariably negative. Kupffer cells of the hamster liver are not stained with Ki-M2R. In the xenografted animals, we found cells in the sinusoidal wall of the xenograft stained, with progressively increased activity, in animals 45-60 days after transplant. The morphological pattern of these Ki-M2R-positive cells in the hepatic xenograft resembled the Kupffer cells of the normal rat liver. These findings indicate recipient macrophage influx into the xenografted liver.