Among 3 neutrophil adhesion substrates, only cell-surface levels of L-selectin are significantly elevated on Adam17^−/− circulating and peritoneal neutrophils. (A-C) Cell-surface levels of Adam17 adhesion substrates CD-44 (A), ICAM-1 (B), and L-selectin (C) were evaluated on circulating and peritoneal neutrophils by flow cytometry. Data are expressed as means ± SD of mean fluorescent intensity. Significant elevation of cell-surface expression of only L-selectin was observed in Adam17^−/− chimeras in both circulating and peritoneal neutrophils (*P = .03 and **P < .01, respectively, n = 5 per group). Multiple replicate experiments showed comparable differences. (D) Representative set of scatter plots is shown (left) for circulating and peritoneal neutrophils (evaluated by CD11b and Ly6G staining) with histograms of percentage of L-selectin⁺ cells from the total Ly6G⁺-gated population (right). Data are shown at 4 hours after thioglycollate injection and without thioglycollate injection for circulating neutrophils.