Molecular and immunohistochemical characterization of the onset and resolution of human renal allograft ischemia-reperfusion injury

Abstract

BACKGROUND Following allotransplantation, renal ischemia-reperfusion (I/R) injury initiates a series of events that provokes counter-adaptive immunity. Though T cells clearly mediate allospecific immunity, the manner in which reperfusion events augment their activation has not been established. In addition, comprehensive analysis of I/R injury in humans has been limited. METHODS To evaluate the earliest events occurring following allograft reperfusion and gain insight into those factors linking reperfusion to alloimmunity, we examined human renal allografts 30 to 60 minutes postreperfusion (n=10) and compared them with allografts with normal function that had resolved their I/R injury insult (>1 month posttransplant, n=6) and to normal kidneys (living donor kidneys before procurement, n=8). Biopsies were processed both for immunohistochemical analysis as well as for transcript analysis by real-time quantitative polymerase chain reaction (RT-PCR). RESULTS Reperfusion injury was characterized by increased levels of gene transcripts known to be involved in cellular adhesion, chemotaxis, apoptosis, and monocyte recruitment and activation. T-cell-associated transcripts were generally absent. However, recovered allografts exhibited increased levels of T-cell and costimulation-related gene transcripts despite normal allograft function. Consistent with these findings, the immediate postreperfusion state was characterized histologically by tubular injury and monocyte infiltration, while the stable posttransplant state was notable for T-cell infiltration. CONCLUSIONS These data suggest that monocytes and transcripts related to their recruitment dominate the immediate postreperfusion state. This gives way to a T-cell dominant milieu even in grafts selected for their stable function and absence of rejection. These data have implications for understanding the fundamental link between I/R injury and alloimmunity.

Histological Alterations Found in the Ureter During Organ Preservation and Early Phases of Renal Transplantation

“…8 The lack of relation to the number of HLA compatibilities suggests that this cellular influx does not seem to involve an immunological phenomena. This is in accordance with the study of Dragun et al who, in the rat, performed renal biopsies after syngeneic and allogeneic renal transplantation with and without immunosuppression and found no significant differences, 11 and with the findings Hoffman et al 7 and Koo et al 8 in postreperfusion renal biopsies in the clinical setting. Cellular vacuolization is known to occur in renal tubular cells after reperfusion 7 and Katz et al 12 considered urothelial vacuolization to be a sign of rejection of the ureter.…”

“…6 In this study, the detection of lymphocytes in the urothelial fragments obtained before reperfusion may be related to the fact that the donors were dead, in concordance with the work of Hoffman et al 7 and of Koo et al, 8 who observed higher cellular infiltration in renal biopsies from cadaveric donors compared with living donors. The inverse relationship between mechanical ventilation length and intensity of cellular infiltration may be related to the fact that mechanically ventilated trauma patients, after an initial rise in the immune response, show a decline, affecting mainly cellular immunity.…”

Human Monocytes as Intermediaries between Allogeneic Endothelial Cells and Allospecific T Cells: A Role for Direct Scavenger Receptor-Mediated Endothelial Membrane Uptake in the Initiation of Alloimmunity

“…Monocytes are drawn to an allograft to some extent in proportion to the degree of reperfusion injury (17). The critical requirement of this cell type for T cell activation described herein helps explain the marked augmentation of alloimmunity that occurs commensurate with aggressive reperfusion injury and monocyte graft infiltration after T cell depletion (16).…”

“…ECs have been shown by many investigators to induce CD4 ϩ T cell proliferation under certain in vitro conditions, specifically when the cells are preincubated with IFN-␥ 2 (43)(44)(45)(46). However, this condition is not consistent with the physiological absence of IFN-␥ at the time of initial monocyte contact with allogeneic EC posttransplant reperfusion (17) and, thus, may not reflect the most likely conditions present during transplantation. Although CD8 ϩ T cells have been shown in vitro to provide IFN-␥ and to stimulate the proliferative capacity of ECs (40), we have shown in humans via serial protocol biopsies that CD8 ϩ T cells are rare in the early infiltrates of renal allografts in depleted hosts (16).…”

“…Indeed, rejection does not occur until monocytes are available in the peripheral circulation, and graft dysfunction occurs upon the arrival at the graft of activated monocytes even without a prominent T cell infiltrate. Monocytes have also been shown to be among the first cells infiltrating human renal allografts immediately upon reperfusion (17,18). Thus, monocytes could be envisioned as interacting with graft cells such as the vascular endothelium and conveying alloantigen and costimulation to T cells.…”