Relative luciferase activity of neutrophil elastase promoter constructs with and without C/EBP site mutation. Constructs tested in CV-1 cells and the myeloid leukemia cell lines Kcl22 and U937. Luciferase activty of the empty vector construct p19Luc was arbitrarily set as 1. (▪) Wild-type; (▨) C/EBP site mutant.