Characterization of IL-17RA^KO neutrophils. (A) IL-17RA^KO neutrophils show no migration defects ex vivo. As a source of chemokines, conditioned media (CM) was obtained from MC3T3-E1 cells stimulated with nothing (Unstim. CM) or 200 ng/mL IL-17 (IL-17 CM; contains > 39 ng/mL LIX; data not shown) for 24 hours (as described¹⁶ ). Bone marrow–derived Gr1⁺ cells from WT (□) or IL-17RA^KO mice (▪) were incubated with media alone, with MC3T3-E1 CM, or with the chemotactic peptide fMLP (100 μM). Cells in the lower chambers were quantified in 10 random microscope fields, and standard deviations are shown. *Significant differences compared with unstimulated samples (P < .001); ‡significant difference between WT and IL-17RA^KO mice for the same treatment condition (P < .01). (B) Normal CXCR2 levels in IL-17RA^KO mice. Bone marrow from WT (black) or IL-17RA^KO (gray) mice was stained with Abs to Gr1 and CXCR2. Cells were gated on the Gr1⁺ population, and the profile of CXCR2 staining is shown compared with the isotype control. (C) Ectopically applied chemokines rescue neutrophil migration to gingiva in IL-17RA^KO mice. WT and IL-17RA^KO mice were anesthetized, and a mixture of LIX and Groα was applied adjacent to the maxillary first molars for 1 hour. Sagittal sections of maxillary tissue were stained with H&E, and neutrophils were assessed by counting in a randomized, blinded fashion. Standard deviations are shown. *Significant differences compared with sham-infected sample by unpaired t test (P < .05).