The Mouse CTLA4[biotin]:B7-1 Inhibitor Screening Assay Kit is designed for screening and profiling inhibitors of mouse CTLA4:B7-1 signaling. The key to this kit is the high sensitivity of detection of biotin-labeled mouse CTLA4 by streptavidin-HRP. Only a few simple steps on a microtiter plate are required for the assay. First, B7-1 is coated on a 96-well plate. Next, CTLA4[biotin] is incubated with B7-1 on the plate. Finally, the plate is treated with streptavidin-HRP followed by addition of an HRP substrate to produce chemiluminescence, which can be measured using a chemiluminescence reader.