Nonreactive monocytosis in p15Ink4b^fl/fl-LysMcre mice. Blood cell counts in p15Ink4b^wt/wt-LysMcre mice (wt/wt, n = 5), in p15Ink4b^fl/wt-LysMcre mice (fl/wt, n = 5), and in p15Ink4b^fl/fl-LysMcre mice (fl/fl, n = 6) at 5 to 7 months (A) and 8 to 10 months (B). WBC indicates white blood cells; MO, monocytes; NE, neutrophils; LY, lymphocytes; PLT, platelets; and RBC, red blood cells. Data are mean ± SD (error bars) for cell concentrations. P values were calculated using the Student t test and only shown where statistically significant. (C) Representative flow cytometric analysis of PB nucleated cells. Monocytes (Gr-1^−/lo/Mac-1⁺) are highlighted in red. (D) May-Grunewald-Giemsa staining of PB from p15Ink4^fl/fl-LysMcre mice with nonreactive monocytosis confirmed increased numbers of mature and maturing mononuclear cells. Scale bar represents 10 μm