Donor and recipient contributions of ICAM-1 and P-selectin in parenchymal rejection and graft arteriosclerosis:: Insights from double knockout mice

Background: Mice with target gene deletions were used in an immunosuppressed, heterotopic mouse cardiac transplant model to investigate the effects of simultaneous deficiencies of ICAM-1 and P-selectin on late cardiac rejection. Methods: To determine the contribution of donor sources of ICAM-1 and P-selectin; ICAM-1/P-selectin gene deficient (I/P -/-) (n = 7) or wild type (n = 6) donor hearts were placed into CBA recipients. To study recipient sources of ICAM-1 and P-selectin, wild type donor hearts were placed into I/P -/- (n = 7) or wild type (n = 13) recipients. Recipients received a 30-day course of anti-CD4/8 mAb. Results: I/P -/- donor allografts had prolonged survival (52-57 days) compared with wild type allografts (49-51 days). I/P -/- donor allografts underwent parenchymal rejection with mononuclear cell infiltration and developed a-smooth muscle actin positive vascular thickening (30 +/- 7% luminal occlusion, n = 78 vessels). Wild type allografts had parenchymal rejection with vascular medial necrosis and an absence of arteriosclerotic thickening (10 +/- 8%, n = 75, p = 0.008). Using the reverse combination, allografts from UP -/- or wild type recipients had similar graft survival (50-57 days), comparable but variable degrees of parenchymal rejection, and comparable vascular occlusion (22 +/- 15% vs 28 +/- 19%, p = 0.442). Conclusion: We have shown that donor and recipient sources of ICAM-1 and P-selectin may have independent roles in leukocyte trafficking to the graft. Simultaneous interruption of donor ICAM-1 and P-selectin delays onset of parenchymal rejection. However, donor I/P deficiency permits arteriosclerotic development, perhaps by attenuating the alloimmune injury. In contrast, recipient deficiency alone does not alter graft outcomes suggesting that the donor is the critical site of ICAM-1 and P-selectin.