Total and CD11b^lo macrophage subsets are greatly reduced before and during E-stress response in Spi-C–deficient and VCAM-1–deficient mice. Numbers of CD11b^lo (lighter shades) and CD11b^hi (darker shades) macrophages, as well as VCAM-1 expression in F4/80⁺ cells in the BM and spleen were determined at several points after PHZ challenge. (A) Spi-C–deficient mice (blue bars and lines, n = 3 for each time point). (B) VCAM-1 knockouts (peach bars and lines, n = 3 to 5 mice for each time point). (C) Normal irradiated recipients transplanted (Tx) with either normal donor cells (red hatched bars) or VCAM-1^−/− donor cells (peach hatched bars, n = 5 for each time point). Red bars and lines represent the respective controls (n = 6 to 12 mice for each time point). Significant difference from control; *P < .05. Note that total F4/80⁺ cells are significantly reduced in mutant mice compared with their controls before and especially after PHZ challenge, mainly in the spleen. Far right panels in (A-B) indicate levels of VCAM-1 expression in total macrophages. Note that less VCAM-1 expression (lower MFI) is seen in Spi-C–deficient and virtually no expression in VCAM-1–deficient macrophages (low MFI VCAM-1 was seen in <10% of F4/80⁺ cells). Ctrl, control; d, day; MFI, mean fluorescence intensity.