EPCR expression in bone marrow–resident macrophages. Flow cytometric characterization of bone marrow–resident EPCR^POS myeloid cells in unchallenged wild-type mice (no LPS) and 16 hours after LPS challenge (34 mg/kg). Scatterplots depict expression of EPCR, c-kit, and Sca-1 in CD45^POS bone marrow cells. Histograms show surface expression of the indicated antigens (red line) in EPCR^POS cell populations in the indicated gates, with blue color indicating the signals obtained with isotype-matched nonimmune antibody. Cells coexpressing EPCR, Gr1, and CD11b express low levels of Sca-1 (as determined by back-gating; not shown).