Defective neutrophil migration to the gingiva in IL-17RA^KO mice. IL-17RA^KO or WT mice were infected with Pg 3 times over 5 days and killed 24 hours after the final inoculation. Sections were stained with H&E. Images were acquired with a Zeiss Axioimager 2I microscope system. (A) At least 80 slides per condition were examined for neutrophils by oil immersion microscopy at ×1000 magnification, and the number of neutrophils normalized to number of teeth present per slide was determined. Standard deviations are shown. Statistical significance of differences between Pg-infected and sham-infected was assessed by unpaired t test (P < .05). (B-C) Sample slides showing neutrophils in representative Pg-infected WT (panel B) or IL-17RA^KO (panel C) gingival slices imaged with 40×/0.10, 200×/0.45, and 1000×/1.30 oil-immersion objective lenses. Arrows indicate polymorphonuclear neutrophils. 1M indicates first molar; 2M, second molar; PDL, periodontal ligament; B, bone; ABC, alveolar bone crest; CEJ, cementoenamel junction; DP, dental pulp; CT, connective tissue; Ep, epithelium; C, capillary; and S, sulcus.