Exogenous G-CSF yields changes similar to neutropenia and reveals transcriptional regulation of G-CSF in the marrow. (A) Marrow flow cytometry in control and rh-G-CSF–treated C57BL/6 mice (n = 5). (B) Absolute marrow cell numbers in both hind limbs of C57BL/6 mice after rh-G-CSF (n = 5) versus PBS (n = 3). rh-G-CSF: p(LSK) < 0.001; p(GMP) = 0.01; p(CMP) = 0.02; p(MEP) < 0.001. (C) Transcriptional G-CSF levels in the marrow of control-, rh-G-CSF–, RB6-8C5–, and 1A8-treated C57BL/6 mice. Note the increase of G-CSF on neutropenia and the negative feedback at the RNA level after application of rh-G-CSF. p(rh-G-CSF) = 0.045; p(RB6-8C5) = NS; p(1A8) = NS.