Apoptosis assay of neutrophils. Neutrophils of wild-type and C/EBPβ-deficient mice were harvested from peritoneal cavity and cultured for 0, 2, 6, and 18 hours with RPMI 1640 and 10% FBS alone (A) or with LPS (100 ng/mL) (B) or GM-CSF (10 ng/mL) (C). Apoptosis was measured by TUNEL assay. Results represent the mean plus or minus SD of 4 mice in each cohort.