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Published online before print August 9, 2007
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From the Lanais de la Facultad de Medicina,* and Sección Hematología y Oncología,
Departamento de Pediatría, Hospital de Clínicas "José de San Martín," Facultad de Medicina, y Departamento de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina; the Department of Pediatrics,
Dalhousie University, Halifax, Nova Scotia, Canada; and the Department of Neurobiology,
David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California
During microbial infection, neutrophils (polymorphonuclear leukocytes; PMNs) activate dendritic cells (DCs). However, early reports illustrated that neutrophil-derived mediators may suppress responses to mitogens. In the present study, we investigated the mechanism used by PMNs to modulate the immunostimulatory ability of DCs. Autologous syngeneic PMNs decreased T-cell proliferation induced by allogeneic DCs. Culture supernatant (CS) derived from PMNs also decreased allostimulation ability of immature DCs and increased the expression of transforming growth factor (TGF)-ß1 on DCs. A TGF-ß1 monoclonal antibody, a CD40 monoclonal antibody, or a serine protease inhibitor reversed the effect of PMN CS on DC allostimulatory ability. Furthermore, elastase reproduced the inhibitory effect of PMN CS on DC allostimulatory ability and the TGF-ß1 production. The role of elastase was confirmed by examining PMN CS from two patients with cyclic neutropenia, a disease due to mutations in the neutrophil elastase gene. These PMN CS samples had reduced elastase activity and were unable to increase DC TGF-ß1 production. Moreover, elastase and PMN CS induced I
B
degradation in DCs. We conclude that PMNs decrease DC allostimulatory ability via production of elastase leading to a switch of immature DCs into TGF-ß1-secreting cells.
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