Caspases play important roles in apoptosis and inflammation. Caspase 8 Assay Kit (Red) (ab270786) is used by researchers seeking to quantitate apoptosis via caspase activity in cultured cells and tissues.

The reagent SR-LETD-FMK enters each cell and irreversibly binds to activated caspase-8. Because the SR-LETD-FMK reagent becomes covalently coupled to the active enzymes, it is retained within the cell, while any unbound SR-LETD-FMK reagent diffuses out of the cell and is washed away. The remaining red fluorescent signal is a direct measure of the active caspase-8 enzyme activity present in the cell at the time the reagent was added. Cells that contain the bound SR-LETD-FMK can be analyzed by a fluorescence plate reader, fluorescence microscopy, or flow cytometry. Cells labeled with the SR-LETD-FMK reagent may be read immediately or preserved for 16 hours using the fixative included in the kit. Unfixed samples may also be analyzed with Hoechst 33342 to detect changes in nuclear morphology.

There is no interference from pro-caspases or inactive forms of the enzymes. If the treatment is causing cell death via apoptosis, apoptotic cells will have an elevated level of caspase activity relative to nonapoptotic or negative control cells and fluoresce with SR-LETD-FMK.