The STAT5 Reporter (Luc)-Ba/F3 cell line is designed for monitoring STAT5 signal transduction pathways. It contains a firefly luciferase gene driven by the STAT5 response element located upstream of the minimal TATA promoter. After activation by cytokines or growth factors, endogenous STAT5 binds to the DNA response elements, inducing transcription of the luciferase reporter gene.