The Interferon Regulatory Factor (IRF) reporter (Luc)-THP-1 cell line is designed to study the activation and signaling of Cytosolic DNA Sensors (CDS) in human monocytic cell line THP-1. It contains a firefly luciferase gene driven by multimerized ISRE (Interferon Stimulated Response Element) located upstream of the minimal TATA promoter. The cGAS-STING pathway acts to detect cytosolic DNA and induce an immune response. Briefly, upon binding DNA, the protein cGAS (cyclic GMP-AMP Synthase) triggers reaction of GTP and ATP to form cGAMP. cGAMP binds to STING (Stimulator of Interferon Genes) which triggers phosphorylation of IRF3 via TBK1. IRF3 can then bind to interferon-stimulated responsive elements (ISRE) in the nucleus and leads to IFN-α/β production. The IRF reporter (Luc)-THP-1 cell line is highly responsive to STING and CDS ligands.