Hypothermic Perfusion Modifies the Association Between Anti-LG3 Antibodies and Delayed Graft Function in Kidney Recipients.

We previously reported associations between autoantibodies to the LG3 fragment of perlecan, anti-LG3, and a higher risk of delayed graft function (DGF) in kidney transplant recipients. Here, we aimed to determine whether some factors that modulate ischemia-reperfusion injury (IRI) can modify this association. We performed a retrospective cohort study in kidney transplant recipients in 2 university-affiliated centers. In 687 patients, we show that high pre-transplant anti-LG3 are associated with DGF when the kidney is transported on ice (odds ratio (OR): 1.75, 95% confidence interval 1.02-3.00), but not when placed on hypothermic perfusion pump (OR: 0.78, 95% CI 0.43-1.37). In patients with DGF, high pre-transplant anti-LG3 are associated with a higher risk of graft failure (subdistribution hazard ratio (SHR): 4.07, 95% CI: 1.80, 9.22), while this was not the case in patients with immediate graft function (SHR: 0.50, 95% CI 0.19, 1.29). High anti-LG3 levels are associated with a higher risk of DGF in kidneys exposed to cold storage, but not when hypothermic pump perfusion is used. High anti-LG3 are also associated with a higher risk of graft failure in patients who experience DGF, a clinical manifestation of severe IRI.

Double Pretransplant Positivity for Autoantibodies to LG3 and Angiotensin II Type 1 Receptor Is Associated With Alloimmune Vascular Injury in Kidney Transplant Recipients.

Both angiotensin II receptor autoantibodies (ATRabs) and autoantibodies to LG3 have been linked to kidney graft rejection with alloimmune vascular injury (AVI). We aimed to examine whether positivity for both anti-LG3 and ATRabs is associated with rejection with AVI in kidney transplant recipients. Methods: We performed a retrospective cohort study including consecutive kidney transplant recipients between 2013 and 2017 at a single center. The primary outcome was acute rejection with AVI (Banff grade 2 or 3 T-cell-mediated rejection and/or antibody-mediated rejection) in the first 3 mo posttransplant. The secondary outcome was death-censored allograft loss. The independent variables, anti-LG3 and ATRab, were measured pretransplant. Results: Among the 328 study participants, 68 experienced acute rejection with AVI and 23 experienced graft loss over a median follow-up of 4.5 y. In a multivariable model, double pretransplant positivity for anti-LG3/ATRab was associated with acute rejection with AVI (odds ratio: 2.73, 95% confidence interval: 1.06-7.05). We did not observe an association between double positivity for anti-LG3/ATRab and death-censored graft loss. Conclusions: Double positivity for anti-LG3/ATRabs pretransplant is associated with a higher risk of acute rejection with AVI. Whether therapies that remove antibodies could decrease that risk remains to be studied.Supplemental Visual Abtract: http://links.lww.com/TXD/A494.

Autolysosomes and caspase-3 control the biogenesis and release of immunogenic apoptotic exosomes.

Apoptotic exosome-like vesicles (ApoExos) are a novel type of extracellular vesicle that contribute to the propagation of inflammation at sites of vascular injury when released by dying cells. ApoExos are characterized by the presence of the C-terminal perlecan LG3 fragment and 20S proteasome, and they are produced downstream of caspase-3 activation. In the present study, we assessed the relative roles of autophagy and caspase-3-mediated pathways in controlling the biogenesis and secretion of immunogenic ApoExos. Using electron microscopy and confocal immunofluorescence microscopy in serum-starved endothelial cells, we identified large autolysosomes resulting from the fusion of lysosomes, multivesicular bodies, and autophagosomes as a site of ApoExo biogenesis. Inhibition of autophagy with ATG7 siRNA or biochemical inhibitors (wortmannin and bafilomycin) coupled with proteomics analysis showed that autophagy regulated the processing of perlecan into LG3 and its loading onto ApoExos but was dispensable for ApoExo biogenesis. Caspase-3 activation was identified using caspase-3-deficient endothelial cells or caspase inhibitors as a pivotal regulator of fusion events between autolysosomes and the cell membrane, therefore regulating the release of immunogenic ApoExos. Collectively, these findings identified autolysosomes as a site of ApoExo biogenesis and caspase-3 as a crucial regulator of autolysosome cell membrane interactions involved in the secretion of immunogenic ApoExos.