(A) Phagocytosis activity of peripheral blood neutrophils. Whole blood collected from wild-type and C/EBPɛ-deficient mice was incubated with FITC-labeled, opsonizedE coli at either 0°C or 37°C for 60 minutes, then accessed by flow cytometry. Panel a shows representative histograms of wild-type and C/EBPɛ-deficient neutrophil samples: thin lines, 0°C incubation; thick lines, 37°C incubations. Panel b summarizes results represented graphically by Box and Whisker graph showing standard deviation, standard error, and mean. (▪) Represent wild-type neutrophils, gray boxes represent C/EBPɛ-deficient neutrophils. An asterisk (*) indicates wild-type neutrophil phagocytosis, as determined by geometric mean of fluorescent intensity, is significantly greater than C/EBPɛ-deficient neutrophils (P< .03, Mann Whitney U). (B) Phagocidal activity of peripheral blood neutrophils. Whole blood collected from wild-type and C/EBPɛ-deficient mice was incubated with titered S aureus, followed by treatment with lysostaphin. At represented time points, aliquots were lysed osmotically, samples streaked on TSA plates, and incubated overnight. Results are represented by Box and Whisker graph showing standard deviation, standard error, and mean. (▪) Represent wild-type neutrophils, gray boxes represent C/EBPɛ-deficient neutrophils. An asterisk (*) indicates wild-type neutrophil bacterial killing is significantly greater than C/EBPɛ-deficient neutrophil killing at 60 minutes (P < .02, Mann Whitney U). (C) Granule protein expression in wild-type and C/EBPɛ-deficient bone marrow. Northern blot hybridization of total RNA harvested from bone marrow, resolved by electorphoresis and transferred to Nytran. Blots were hybridized with ³²P-–dCTP-labeled granule protein probes. C/EBPɛ-deficient neutrophil RNA (−/−); wild-type (+/+). Equivalent sample loading is shown by 18S bands.