The CD71/TfR Colorimetric Cell-Based ELISA Kit provides a lysate-free, convenient, and high-throughput approach for sensitive detection of CD71/TfR protein expression profile in cells. The kit can be used for measuring the relative amounts of CD71/TfR in cultured cells as well as screening for the effects that various treatments, inhibitors (ie siRNA or chemicals), or activators have on CD71/TfR.