HU attenuates neutrophil adhesion and migration. (A) Neutrophil recruitment to the lung in response to killed pneumococci administered intratracheally was quantitated by FACS of bronchoalveolar lavage from saline- and HU-treated SCA mice 6 hours after challenge (n = 6 mice/group; PBS 26.2 ± 16.8, HU = 5.16 ± 3.00; * P < .05 compared with SCA by Mann-Whitney). Data represent percentage of total cells isolated from bronchoalveolar lavage. (B) SCA mice ± HU were exposed to intravenous TNFα to induce endothelial activation and neutrophil margination. Neutrophil adherence was quantitated in cranial windows (5 minutes at ×40 per mouse for at least 4 mice/group; *P < .05 compared with SCA by Mann-Whitney). (C-D) Representative images through cranial windows on SCA (C) or SCA + HU (D) mice. Neutrophils indicated by arrows, ×10 magnification. (E-F) Representative images of GFP neutrophils (green) imaged by 2-photon microscopy in the rhodamine-dextran–labeled vasculature (red) of SCA mice (E) and SCA mice treated with HU (F).