Activation of coagulation in lethal influenza A infection. Activation of coagulation in lethal influenza A infection. Levels of a, c) thrombin-antithrombin complex (TATc) and b, d) fibrin degradation product (FDP) in a, b) lung and c, d) plasma at baseline, and 48 and 96 h after induction of lethal influenza A infection in wild-type mice (□) and mice heterozygous (░) or homozygous (▒) for the factor V Leiden mutation. Data are expressed as box-and-whisker diagrams depicting the smallest observation, lower quartile, median, upper quartile and largest observation. **: p<0.01 compared to baseline; ***: p<0.001 compared to baseline (Mann–Whitney U-test). M. Schouten et al. Eur Respir J 2010;36:1346-1354 ©2010 by European Respiratory Society