This nuclear receptor assay system utilizes proprietary non-human mammalian cells engineered to provide constitutive, high-level expression of human farnesoid X receptor (NR1H4), a ligand-dependent transcription factor commonly referred to as FXR. INDIGO’s reporter cells include the luciferase reporter gene functionally linked to an FXR-responsive promoter. Thus, quantifying changes in luciferase expression in the treated reporter cells provides a sensitive surrogate measure of the changes in FXR activity. The principal application of this reporter assay system is in the screening of test samples to quantify any functional activity, either agonist or antagonist, that they may exert against human FXR. FXR reporter cells are prepared using INDIGO’s proprietary CryoMite™ process. This cryo-preservation method yields exceptional cell viability post-thaw, and provides the convenience of immediately dispensing healthy, division-competent reporter cells into assay plates. There is no need for cumbersome intermediate treatment steps such as spin-and-rinse of cells, viability determinations, cell titer adjustments, or the pre-incubation of reporter cells prior to assay setup. INDIGO Bioscience’s nuclear receptor reporter assays are all-inclusive cell-based assay systems. In addition to FXR reporter cells, this kit provides two optimized media for use during cell culture and in diluting the user’s test samples, a reference agonist, luciferase detection reagent, and a cell culture-ready assay plate.