The initial contact point between a recipients immune system and a transplanted graft is the vascular endothelium. Our goal is to identify the antigenic targets of anti-endothelial cell antibodies (AECAs) and the mechanisms they employ to elicit allograft rejection.
Antibody analysis was performed using solid-phase HLA-bead assays and flow cytometric crossmatch tests using lymphocytes and endothelial cell precursors as target cells. AECA IgG subclass determination was performed using flow cytometry and subclass specific monoclonal antibodies. Endothelial cell activation, following stimulation with AECAs or control serum, was analyzed by flow cytometry. Antigenic targets for the AECAs were identified using high-density protein arrays and confirmed using immunohistochemistry.
Characterization of AECAs was performed using sera from ten renal transplant recipients with histologic features of antibody mediated rejection (glomerulitis and peritubular capillary margination) and graft dysfunction in the absence of identifiable donor-specific HLA antibodies and C4d deposition. These sera tested positive in donor-specific endothelial cell crossmatch tests and the AECAs were shown to be enriched for IgG2 and IgG4; subclasses inefficient in activating complement. AECA stimulation of endothelial cells isolated from large vessels and glomerular microvasculature showed increased expression of HLA class I and adhesion molecules: PECAM1, ICAM1, and E selectin when compared to stimulation with negative control serum. Analysis of AECAs using high-density protein arrays identified three novel antigenic targets expressed on endothelial cells. Expression of these target antigens was confirmed in renal biopsies taken at the time of rejection.
This study describes three previously unidentified targets of AECAs. Antibodies to these antigens where shown to activate endothelial cells in vitro, resulting in the up regulation of HLA antigens and adhesion molecules. These changes may increase trafficking of immune cells into the allograft in the absence of complement activation, explaining the histology observed in the biopsies. These findings provide potential avenues for developing successful rejection therapy strategies.
Jackson, A.: Other, Olerup Inc. Travel Expenses.
To cite this abstract in AMA style:Jackson A, Sigdel T, Bagnasco S, Montgomery R, Sarwal M. Endothelial Cell Reactive Antibodies: Antigenic Targets and Mechanism of Action [abstract]. Am J Transplant. 2013; 13 (suppl 5). https://atcmeetingabstracts.com/abstract/endothelial-cell-reactive-antibodies-antigenic-targets-and-mechanism-of-action/. Accessed May 6, 2021.
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