Surface expression of HSP72 by LPS-stimulated neutrophils facilitates γδT cell-mediated killing

During inflammation and sepsis, accumulation of activated neutrophils causes lung tissue damage and organ failure. Effective clearance of neutrophils reduces the risk of organ failure; however, its mechanisms are poorly understood. Because lungs are rich in gamma delta T cells, we investigated the physiological role of these cells in the protection of lung tissue from infiltrating neutrophils. in a mouse model of sepsis, we found that the lungs of survivors contained significantly higher numbers of gamma delta T cells than those of mice that died from sepsis. The number of gamma delta T cells correlated inversely with the number of neutrophils in the lungs and with the degree of lung tissue damage. LPS rapidly elicited the expression of heat shock protein (HSP) 72 on the surface of human neutrophils. Inhibitors of transcription, protein synthesis, and intracellular protein transport blocked HSP72 expression, indicating that de novo synthesis is required. gamma delta T cells targeted and rapidly killed LPS-treated neutrophils through direct cell-to-cell contact. Pre-treatment with neutralizing antibodies to HSP72 diminished neutrophil killing. Our data indicate that HSP72 expression on the cell surface predisposes inflamed neutrophils to killing by gamma delta T cells. This intercellular exchange may allow gamma delta T cells to resolve inflammation and limit host tissue damage during sepsis.