Release of CXCL1-containing granules by mast cells in vivo after LPS stimulation. Consecutive sections of peritoneal wall tissue obtained 1 hour after IP injection of (A) PBS or (B) LPS into WT mice. The sections were stained with toluidine blue (mast cells), with MAC-2 (Mph) or anti-CXCL1 mAbs. Arrows indicate mast cells or macrophages overlapping with CXCL1-expressing cells. The immunostaining is representative of tissues from n = 4 mice. (C) Percentage of mast cells displaying CXCR1 granules in peritoneal wall sections of mice treated with either PBS or LPS over time. Mean ± SEM of 1 experiment of 2 is shown with each group representing 3 mice. (D) Percentage of mast cells displaying CXCR1 granules in peritoneal tissue (top panel) and recruited neutrophils in peritoneal lavage (bottom panel) after IP injection of LPS or PBS over 4 hours. Data represent mean ± SEM from n = 3 experiments with each data point representing n = 8 mice. *P < .05; **P < .01; and ***P < .001. Mph, macrophage; V, vessel.