FIG 3.

Respiratory VACV-WR infection induces NK cell activation and proliferation. Wild-type C57BL/6J (WT) mice were intranasally infected with 1.25 × 10⁴ PFU of VACV-WR. On the indicated days postinfection, lung, spleen, and bone marrow (BM) NK cells (CD3⁻ NKp46⁺ NK1.1⁺) were examined for phenotypic and functional markers by flow cytometry. (A) Expression of CD11b and CD27 by gated CD3⁻ NKp46⁺ NK1.1⁺ cells in mock-infected (day zero [D0]) and VACV-infected mice. The quadrants show the three major NK subsets (CD11b^low CD27^high, CD11b^high CD27^high, and CD11b^high CD27^low). (B) Representative FACS plots showing the percentages of NK cell proliferation by Ki67 staining among CD3⁻ NKp46⁺ NK1.1⁺ cells in mock-infected (D0) and VACV-infected mice. The numbers in the plots indicate the percentages of NK1.1⁺ cells that stained for Ki67. (C) Representative FACS plots showing cell surface expression levels of CD69, CD44, CD43, and KLRG by lung NKp46⁺ NK1.1⁺ cells on day 5 postinfection. The results shown are representative of three experiments each with three mice per group.