Mitochondrial damage-associated molecular patterns activate γδ T-cells

Gamma delta T-cells have been shown to be important in the early immunoinflammatory response to injury, which can be independent of infection. This sterile inflammatory response is believed to be, in part, associated with danger-associated molecular patterns (DAMPs). Mitochondrial DAMPs (MTDs) have been shown to be important in trauma-induced neutrophil activation, but it is unknown whether MTDs activate other innate immune cells, such as γδ T-cells. To study this, splenic CD3+ γδ T-cells were isolated from αβ T-cell-deficient C57BL/6 mice and mitochondria isolated from wild type mouse livers. MTDs were isolated from mitochondria by sonication and centrifugation. Gamma delta T-cells were incubated with various concentrations of MTDs (0-500 μg/ml) for 24 h. T-cells were phenotyped for TLR expression by flow cytometry and the supernatants assayed for cytokine and growth factor content. MTDs caused a dose-dependent increase in TLR2 and TLR4 expression by γδ T-cells. Both the percentage of cells positive for TLRs and the degree of expression increased. MTDs also induced the production of IL-1β, IL-6, IL-10, RANTES, fibroblast growth factor-basic and vascular endothelial growth factor by γδ T-cells. These findings support the concept that the MTDs released after tissue/cellular injury are capable of activating γδ T-cells, thus initiating sterile inflammation, as well as subsequent healing processes.