Northern blot analysis of the 4 neutrophil cell populations after MACS purification. (A) Northern blot of total RNA from the 4 MACS-depleted cell populations. The blot was hybridized with probes against the granule proteins MPO, lactoferrin, and fMLP-R, which are expressed specifically in MBs/PMs, MCs/MMs, and BCs/SCs and PMNs, respectively. (B) Schematic representation of the hybridization intensities from panel A. For each probe, the cell population showing maximal expression is given the value 1; the expression levels in the other cell populations are shown relative to this. All expression levels are normalized to the 18S level. (C) Relative hybridization intensities of 18S and β-actin in the 4 cell populations. Data are based on 12 (18S) or 17 (β-actin) filters blotted with 5 μg RNA from each cell population. For each hybridization, the cell population with the strongest signal was given the value 1, and the other signal intensities were related to this.