Figure 1. Up-regulation of hepatic B7-H1 expression with cold I/R injury after mouse liver transplantation (LTx).

(A) B7-H1 mRNA levels in liver graft samples. Liver graft tissues were harvested 1, 3, 6 and 12 hr after WT to WT LTx with 24 hr cold ischemia and analyzed by RT-PCR (n=3). Whole liver tissue from normal mice was used as control and values are expressed as fold increases. B7-H1 mRNA increased at 3 hr and peaked at 6 hr.

(B) B7-H1 mRNA levels in hepatocytes and non-parenchymal cells (NPC). Parenchymal cells and NPC were isolated after collagenase digestion as described in the Materials and Methods, at 3 and 6 hr after WT to WT LTx with 24 hr cold ischemia and analyzed by RT-PCR (n=3). B7-H1 message was detected in both hepatocyte and NPC fractions, with a significantly higher increase after LTx in parenchymal cells (*p<0.05).

(C) B7-H1 protein expression on hepatocytes, DC and sinusoidal endothelial cells (SEC). Liver NPC and hepatocytes were isolated 6 hr after WT to WT or B7-H1 KO to WT LTx with 24 hr cold preservation and analyzed for cell surface B7-H1 expression by flow cytometry. In normal naive mice, B7-H1 was expressed on CD11c⁺ dendritic cells (DC) and CD31⁺ SEC, but not on hepatocytes. After WT to WT LTx, B7-H1 was up-regulated on all of these cell types. By contrast, in KO to WT LTx, B7-H1 was not expressed on hepatocytes or SEC, although there was slight B7-H1 positivity on DC (most likely due to infiltrating host WT DC). Data are representative of three independent experiments.