Quiescent HSCs are resistant to infection by bacteria.

(A) Fluorescence microscopic image. Detection of CD34⁺ HSCs (stained with anti–CD34-PE antibodies) and extracellular, green fluorescent L monocytogenes(arrowheads) carrying the gfp gene under control of the constitutively active sod promotor (1 hour after infection; bar, 10 μm). (B) Light microscopic image of the identical field (1 hour after infection; bar, 10 μm); bacteria are marked with arrowheads. (C) No uptake of Y enterocolitica in quiescent HSCs (Giemsa staining at 24 hours after infection; bar, 10 μm).