CD3+CD4-CD8- Double-negative αβ T cells attenuate lung ischemia-reperfusion injury

Objective: Lung ischemia-reperfusion injury (IRI) is a common complication after lung transplantation, and immune cells have been implicated in modulating outcomes. We hypothesized that a newly described subset of alpha beta T-cell receptor positive cells; that is, CD4(-)CD8(-) (double negative [DN]) T cells, are found in lungs and can protect against lung IRI. Methods: Ischemia was induced in C57BL/6 mice by left pulmonary artery and vein occlusion for 30 minutes followed by 180 minutes of reperfusion. These mice were paired with sham hilar dissected surgical controls. In mice undergoing IRI, adoptive transfer of DN T cells or conventional T cells was performed 12 hours before occlusion. Flow cytometry was used to quantify T cells and inflammatory cytokines, and apoptotic signaling pathways were evaluated with immunoblotting. Lung injury was assessed with Evans blue dye extravasation. Results: DN T cells were significantly higher (5.29% +/- 1% vs 2.21% +/- 3%; P < .01) in IRI lungs and secreted higher levels of interleukin-10 (30% +/- 5% vs 6% +/- 1%; P < .01) compared with surgical sham controls. Immunoblotting, hematoxylin and eosin staining and Evans blue dye demonstrated that adoptive transfer of DN T cells significantly decreased interstitial edema (P < .01) and attenuated apoptosis/cleaved caspase-3 expression in the lungs following lung IRI (P < .01). Conclusions: DN T cells traffic into lungs during IRI, and have tissue protective functions regulating inflammation and apoptosis. We propose a potential novel immunoregulatory function of DN T cells during lung IRI.