L-selectin down-regulation by neutrophils from ADAM17^ΔZn/ΔZn- and ADAM17^+/+-chimeric mice following spontaneous apoptosis. (A) Bone marrow neutrophils from the indicated mice were cultured for approximately 24 hours, and then triple-stained for surface expression of L-selectin, neutrophil marker Ly-6G, and annexin V–FITC. Relative staining levels were determined by flow cytometry. The contour plots represent gated neutrophils, and the x- and y-axes indicate log-10 fluorescence. (B) Bone marrow neutrophils from the ADAM17^ΔZn/ΔZn (ΔZn/ΔZn)– and ADAM17^+/+ (+/+)–chimeric mice were cultured for approximately 24 hours in the presence or absence of the metalloprotease inhibitor TAPI-0, as indicated. Media supernatant was then collected and passed through a syringe filter to remove membrane fragments larger than 0.22 μm. The presence of soluble L-selectin in the media was determined by ELISA analysis, as described in “Materials and Methods.” Neutrophils from the ADAM17^ΔZn/ΔZn- and ADAM17^+/+-chimeric mice were plated in triplicate wells, and the supernatant from each well was analyzed in duplicate. Each bar represents the mean ± SD. *P < .01 versus ADAM17^+/+ plus TAPI-0; #P < .01 versus ADAM17^ΔZn/ΔZn plus TAPI-0. Data are representative of 3 independent experiments.