Double-negative T cells have a reparative role after experimental severe ischemic acute kidney injury

T cells mediate organ injury and repair. A proportion of unconventional kidney T cells called double-negative (DN) T cells (TCR+ CD4- CD8-), with anti-inflammatory properties, were previously demonstrated to protect from early injury in moderate experimental AKI. However, their role in repair after AKI has not been studied. We hypothesized that DN T cells mediate repair after severe AKI. C57B6 mice underwent severe (40min) unilateral ischemia-reperfusion injury (IRI). Kidney DN T cells were studied by flow cytometry and compared to gold-standard anti-inflammatory CD4+ Tregs. In vitro effects of DN T cells and Tregs on renal tubular epithelial cell (RTEC) repair after injury were quantified with live-cell analysis. DN T cells, Tregs, CD4 or vehicle were adoptively transferred after severe AKI. Glomerular filtration rate (GFR) was measured using FITC-sinistrin. Fibrosis was assessed with Masson's trichrome staining. Profibrotic genes were measured with qRT-PCR. Percentages and the numbers of DN T cells substantially decreased during repair phase after severe AKI, as well as their activation and proliferation. Both DN T cells and Tregs accelerated RTEC cell repair in vitro. Post-AKI transfer of DN T cells reduced kidney fibrosis and improved GFR, as did Treg transfer. DN T cell transfer lowered TGFβ1 and αSMA expression. DN T cells reduced effector-memory CD4+ T cells and IL-17 expression. DN T cells undergo quantitative and phenotypical changes after severe AKI, accelerate RTEC repair in vitro as well as improve GFR and renal fibrosis in vivo. DN T cells have potential as immunotherapy to accelerate repair after AKI.