Double-negative αβ T cells are early responders to AKI and are found in human kidney

Ischemia-reperfusion injury (IRI) is a major cause of AKI, and previous studies established important roles for conventional CD4⁺ T cells, natural killer T cells, and CD4⁺CD25⁺FoxP3⁺ Tregs in AKI pathogenesis. We recently identified CD4^-CD8^- (double-negative; DN) T cells as an important subset of αβ T cell receptor–positive cells residing in mouse kidney. However, little is known about the pathophysiologic functions of kidney DN T cells. In this study, we phenotypically and functionally characterized murine kidney DN T cells in the steady state and in response to IRI. Unlike CD4⁺ and CD8⁺ T cells, DN T cells in the steady state expressed high levels of CD69, CD28, and CD40L; differentially expressed IL-27 and IL-10 anti-inflammatory cytokines; spontaneously proliferated at a very high rate; and suppressed in vitro proliferation of activated CD4⁺ T cells. Within the first 3–24 hours after IRI, kidney DN T cells expanded significantly and upregulated expression of IL-10. In adoptive transfer experiments, DN T cells significantly protected recipients from AKI by an IL-10–dependent mechanism. DN T cells also made up a large fraction of the T cell compartment in human kidneys. Our results indicate that DN T cells are an important subset of the resident αβ⁺ T cell population in the mammalian kidney and are early responders to AKI that have anti-inflammatory properties.