FIG 4.

NK cells express cytolytic effector molecules and release IFN-γ after respiratory VACV-WR infection. Wild-type C57BL/6J (WT) mice were intranasally infected with 1.25 × 10⁴ PFU of VACV-WR. On day 4 postinfection, total lung (left) and spleen (right) cells were stained for cell surface expression of NK1.1⁺, NKp46⁺, and intracellular granzyme (A) and CD107a (B). Uninfected (naive) mice (day 0) were used as controls. The numbers displayed in quadrants within the zebra plots indicate the percentages of granzyme B- or CD107a-positive cells. On days 3 and 7 postinfection, total lung (C) and spleen (D) cells were stimulated ex vivo with either PMA-ionomycin or IL-12 plus IL-18 and subsequently stained for intracellular IFN-γ. Representative zebra plots for IFN-γ staining by CD3⁻ NK1.1⁺ NKp46⁺-gated NK cells are shown. The numbers in the plots indicate the percentages of NK1.1⁺ NKp46⁺ cells that stained for IFN-γ⁺. Quadrant settings were based on the results for infected cells that were not stimulated with PMA-ionomycin or IL-12 plus IL-18 (medium alone). Similar results were obtained in three separate experiments.