Abstract: TH-OR100
Defining Molecular Mechanisms in Antibody-Mediated Rejection Using Unbiased Proteomics in Donor-Specific Antibody-Positive and -Negative Recipients
Session Information
- Transplantation: Basic and Translational Advances
October 24, 2024 | Location: Room 25, Convention Center
Abstract Time: 04:30 PM - 04:40 PM
Category: Transplantation
- 2101 Transplantation: Basic
Authors
- Allen, Maya A., University of Toronto Temerty Faculty of Medicine, Toronto, Ontario, Canada
- Manion, Kieran, Toronto General Research Institute, Toronto, Ontario, Canada
- John, Rohan, University Health Network, Toronto, Ontario, Canada
- Konvalinka, Ana, University Health Network, Toronto, Ontario, Canada
Background
Kidney transplantation is the optimal treatment for patients with end-stage kidney disease. Unfortunately, many kidney allografts fail prematurely due to antibody-mediated rejection (AMR). AMR is caused by donor-specific antibodies (DSAs) against human leukocyte antigens (HLA) on the graft endothelium. DSAs may cause injury through endothelial activation, complement activation, or interactions with Fcγ receptors (FcγRs) on immune cells. Intriguingly, 30-60% of DSA-positive kidney allograft recipients never develop rejection, and 30-50% of patients that exhibit AMR do not have any detectable DSAs, suggesting the presence of unidentified contributors to the pathogenicity of AMR. Our goal is to define the molecular mechanisms of AMR and uncover these underlying contributors to injury.
Methods
Indication biopsies from 115 patients with DSA+AMR, DSA-AMR, no rejection despite having DSAs (DSA+NR), and T cell mediated rejection (TCMR) were subjected to unbiased proteomics analysis using LC-MS/MS on Q-Exactive mass spectrometer. Significance between groups was established using ANOVA, with p<0.05 considered significant.
Results
We analyzed the glomerular and tubulointerstitial compartments of each biopsy separately. Of the 1203 proteins quantified in the tubulointerstitium, 30 were significantly differentially expressed, and of the 628 quantified in the glomeruli 15 were significantly differentially expressed (ANOVA, p<0.05). Importantly, the expression of complement factors was increased in DSA-AMR tubulointerstitium when compared to DSA+AMR and DSA+NR. However, in the glomeruli complement proteins were dominant in DSA+ AMR. Furthermore, proteins downstream of FcγR activation and phagocytosis were increased in the glomeruli of DSA-AMR and DSA+AMR biopsies when compared to DSA+NR. In the tubulointerstitium, proteins implicated in phagocytosis were highest in DSA-AMR.
Conclusion
The differential expression of complement proteins and proteins implicated in FcγR-mediated phagocytosis suggests distinct patterns of injury in the two kidney compartments and an unanticipated role of complement and phagocytosis in DSA-AMR.