Flagellin induces LSK cell proliferation in vivo. Eight-week-old female C57BL/6 mice were treated with PBS only or with PBS containing 20 μg flagellin by IP injection. Fifteen hours following injection, the mice were labeled with 1 mg BrdU for 1 hour and then euthanized. Whole bone marrow cells were prepared and analyzed by flow cytometry. Representative flow cytometry plots comparing LSK cell proliferation (A), statistical analysis of LSK cell percentage in bone marrow (calculated by forward-side scatter gate % × single cell % × Lin⁻ % × LSK % in Lin⁻ cells) (B), LSK cell number (C), and BrdU incorporation in LSK cells (D) are shown. Statistics were analyzed by unpaired Student t test (**P < .01; ***P ≤ .001). Error bars represent standard error of the mean (SEM). BM, bone marrow; FSC, forward scatter.