(A, right) Northern blot analysis of gp91 phox expression from C/EBPɛ−/− and wild-type bone marrow cells. RNA from NIH 3T3 fibroblasts was used as negative control. Gp91 phox expression was not reduced in C/EBPɛ−/− bone marrow cells. Hybridization with a beta actin probe was used as a control for equal loading of samples. (A, left) RT-PCR assays to determine expression of the p22 phox, p40 phox, p47 phox, p67 phox and (B) rac-1 and -2 genes. Primers for GAPDH were used to test the integrity of the cDNAs. All genes were expressed in both wild-type and C/EBPɛ−/− bone marrow cells. (C) Western blot comparing the protein expression of gp91 phox and p47 phox in wild-type and C/EBPɛ−/− phagocytes collected at either 12 or 72 hours after intraperitoneal injection of 4% thioglycollate into the peritoneal cavity of wild type and C/EBPɛ−/− mice. The mean percentage of granulocytes and monocytes in the samples were at 12 hours: Wild-type, 70/30; C/EBPɛ−/−, 56/44 and at 72 hours: Wild-type, 75/25; C/EBPɛ−/−, 6/94. GAPDH expression was a control for equal loading. The reduction of p47 phox expression was found in 3 independent experiments. The figure depicts the results of a representative experiment.