The Rel (Phospho-Ser503) Cell-Based ELISA Kit is a convenient, lysate-free, high throughput and sensitive assay kit that can monitor Rel (Phospho-Ser503) protein expression profile in cells. The kit can be used for measuring the relative amounts of Rel (Phospho-Ser503) in cultured cells as well as screening for the effects that various treatments, inhibitors (ie. siRNA or chemicals), or activators have on Rel (Phospho-Ser503). Range: > 5000 Cells. Sensitivity: >5000 cells