Flagellin treatment preferentially induces hematopoietic progenitor cell proliferation in bone marrow. Bone marrow cells from WT B6 mice treated with flagellin for 15 hours were analyzed by flow cytometry using antibodies including SLAM-code CD48 and CD150 to determine hematopoietic stem cell and hematopoietic progenitor cell proliferation. The following markers were used: LT-HSCs, CD34⁻Flt3⁻CD150⁺CD48⁻; ST-HSCs, CD34⁺Flt3⁻CD150⁻CD48⁻; MPP1, CD34⁺Flt3^-CD150⁺CD48⁻; MPP2, CD34⁺Flt3⁻CD150⁺CD48⁺; MPP3, CD34⁺Flt3⁻CD150⁻CD48⁺; and MPP4, CD34⁺Flt3⁺CD150⁻CD48⁺. Shown are BrdU incorporation of MPP1, MPP2, MPP3, ST-HSCs (A), and MPP4 (B) in PBS- vs flagellin-treated mice, statistics of total LSK cell number (C); LT-HSC, ST-HSC, MPP1, MPP2, MPP3, and MPP4 cell numbers (D); and BrdU incorporation (E) in PBS- vs flagellin-treated mice. Statistics were analyzed by unpaired Student t test (**P < .01; ***P ≤ .001). Error bars represent SEM. BM, bone marrow.