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Background: It has recently been shown that treatment of animals with antibodies to CD154 (CD40L), allows for prolongation of cardiac allograft survival, but does not inhibit development of graft vasculopathy. CD8+ T cells have been implicated in this effect. In this study we assess the role of CD40–CD154 interactions and CD40-independent CD8+ T cells in the permanent and complete absence of CD40 by using donors and recipients genetically deficient in CD40. Methods: Hearts from BALB/c CD40−/− donors were transplanted into C57BL/6 CD40−/− recipients in the presence or absence of CD8+ T-cell depletion. At Day 60, hearts were examined for vasculopathy using quantitative morphometry and numbers of infiltrating T cells were counted. The intragraft expression of interferon-γ (IFN-γ), transforming growth factor-β1 (TGF-β1), interleukin-4 (IL-4), eotaxin and CCR3 was assessed using competitive reverse transcription–polymerase chain reaction (RT-PCR). Results: In the absence of CD8+ T-cell depletion, the mean percent intimal occlusion was 28% (with 50% of vessels showing no intimal occlusion). This figure was reduced significantly to 12% and 80% of vessels showing no intimal occlusion in mice receiving anti-CD8 antibody. Depletion of CD8+ T cells was associated with significantly reduced intragraft IFN-γ, TGF-β1 and CCR3 expression, whereas mRNA production of IL-4 and eotaxin was increased. Conclusion: Vascular intimal occlusion progresses in the complete absence of CD40–CD154 interactions, albeit to quite a small degree. The residual disease is significantly reduced by anti CD8+ T-cell treatment, confirming the importance of CD40–CD154-independent CD8+ T cells in the genesis of this disease.

Background: ICAM-1 and P-selectin are molecules that facilitate adhesion of circulating leukocytes to vessel walls. We have investigated the role of donor-derived ICAM-1 and P-selectin in acute and chronic cardiac allograft rejection. Methods C57BL/6J (H-2 b ) mice were used as donors for heterotopic heart transplantation into CBA/Ca (H-2 k ) recipients. The donors were wild-type or homozygous for gene mutations of ICAM-1 or P-selectin. We measured acute rejection in non-immunosuppressed recipients by daily palpation and sacrificed mice at Days 2, 4, and 6 for immunohistochemical analysis. For chronic rejection, recipients received monoclonal antibody against CD4+ T cells. We removed hearts at Days 60 to 62 for histologic assessment of vasculopathy using quantitative morphometry to measure intimal thickening. Results Time (days) to rejection was 7.1 ± 0.57 for wild-type ( n = 10), 7.0 ± 0.71 for ICAM-1 −/− (not significantly different, n = 7) and 6.1 ± 0.33 ( p = 0.001) for P-selectin −/− donors. ICAM-1 deficiency was associated with delayed infiltrate at Day 4 compared with wild-type. In the model of chronic rejection, elastin-positive vessels showed a mean occlusion of 34% ± 3% in transplanted wild-type hearts; vessels were divided into those showing 0% to 20%, 20% to 50%, and 50% to 100% occlusion. We observed no difference in the number of affected vessels or the amount of vascular thickening in donors lacking ICAM-1 or P-selectin compared with wild-type controls. Conclusions The absence of ICAM-1 or P-selectin in donor tissues neither lengthens the time of allograft survival nor inhibits the vascular lesions associated with chronic rejection. Indeed, the absence of P-selectin may exacerbate alloimmune injury.

Background . Adhesion of blood elements to the endothelium is an important step in the development of vein graft disease. This study examines the expression of vascular adhesion molecules on explanted saphenous vein bypass grafts. Methods . Immunocytochemical staining was performed using explanted saphenous vein grafts from 28 patients. Antibodies against the endothelial markers CD31, von Willebrand factor, intercellular adhesion molecule-1, vascular adhesion molecule-1, and E-selectin were used. Results . Staining for CD31 and von Willebrand factor demonstrated the presence of endothelial cells in the lumen and the vasa vasorum. Expression of intercellular adhesion molecule-1 was variable between grafts, whereas vascular adhesion molecule-1 and E-selectin were almost always absent on the luminal endothelium. In contrast, the endothelium of the vasa vasorum stained positively for intercellular adhesion molecule-1 and vascular adhesion molecule-1, and was also seen on nonendothelial cells within the vessel wall. Expression of these adhesion molecules did not vary with the severity of vein graft disease. Conclusions . This study highlights the blood vessels in the adventitia as possible sites for the adhesion and migration of cells into the vessel wall.