????T CELLS USE HEAT SHOCK PROTEIN 72 ON THE CELL SURFACE TO KILL ACTIVATED PMN

Abstract

γδT cells down-regulate inflammation by the production of anti-inflammatory cytokines and elimination of inflammatory cells. These responses are critical to limit of organ injury in trauma victims and septic patients. In the present study we investigated the mechanisms by which γδT cells eliminate inflammatory neutrophils (PMN). γδT cells isolated from human blood were co-cultured with autologous PMN in the presence or absence of LPS. Surface phenotype and viability of PMN were assayed by flow cytometry. Cell-to-cell interactions were observed by microscopy. γδT cells targeted and rapidly killed LPS-treated PMN through direct cell-to-cell contact. Exposure to LPS increased this process by 2.2-fold (p=0.038; Figure). LPS induced a 11.2-fold increase in γδT cell CD69 expression and sensitized PMN to γδT cell attack by rapid induction of heat shock proteins (Hsp) 72 on the cell surface. Inhibitors of transcription, protein synthesis, and intracellular protein transport blocked Hsp72 expression, indicating that de novo synthesis is required. Pre-treatment with neutralizing antibodies to Hsp72 significantly reduced the inflammatory PMN killing (p=0.012), suggesting that Hsp72 expression on the cell surface of inflammatory PMN serves as target for cell killing by γδT cells. We conclude that Hsp72 mediated elimination of PMN by γδT cells facilitates the resolution of inflammation and limits host tissue damage in sepsis.FigureSupported in part by grants from NATO, USAMRMC, and NIGMS.