Interaction of neutrophils with interstitial collagen fibers. (A) Representative multiphoton in vivo microscopy images of interstitial collagen fibers (yellow) in the mouse ear 3 hours upon exposure to PBS or PAF. (B) Representative multiphoton in vivo microscopy images of FITC dextran leakage (green) and interstitial collagen fibers (blue) in the PAF-stimulated mouse ear of mice depleted from neutrophils or of control mice. Remodeling events within the interstitial tissue and FITC dextran leakage were quantified, as detailed in the “Methods” section. (C) Results for PBS-treated control mice as well as for mice stimulated with PAF (mean ± SEM for n = 3 per group; #P < .05 vs PBS). (D) Results for mice treated with a neutrophil-depleting anti-Ly6-G antibody or isotype control undergoing stimulation with PAF (mean ± SEM for n = 3 per group; *P < .05 vs isotype control). (E) Results for mice undergoing 240 minutes of stimulation with histamine (mean ± SEM for n = 3 per group). (F) Representative migration tracks (black) of neutrophils (white) within the interstitial tissue. Areas of low (blue), intermediate (yellow), and high (red) collagen density are indicated in pseudocolors (see supplemental Video 1A-D). (G) Representative serial images of an interstitially migrating neutrophil (green) encountering collagen fibers (white; also see supplemental Video 2). Scale bar = 20 μm.