Depletion of neutrophils abrogates MMP9 secretion after influenza virus infection. Neutrophils were depleted by injecting C57BL/6 mice with 400 µg anti-Ly6G antibody (αLy6G) or isotype control (IgG) one day before infection and every other day thereafter. (A) Depletion of Ly6G+ cells in αLy6G-treated C57BL/6 mice ( bottom panel ) compared to IgG ( top panel ) was verified by flow cytometric analysis 6 days after infection. (B) Kinetics of weight loss as a percentage of starting weight in uninfected (control, open symbols ) and infected ( closed symbols ) mice treated with the αLy6G ( squares ) or IgG isotype ( circles ). (C) MMP9 secretion by cells from BAL and lung from infected mice that were treated with αLy6G ( clear bars ) or IgG isotype ( grey bars ) was measured by ELISPOT. (D) Inflammatory cytokine release in airways after neutrophil depletion. BALs were collected 6 days after infection and supernatants assayed by bead array. (B–D) Mean ± SEM (n = 3, representative of two independent experiments). (B–C) Considered significant at * P
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