Annexin V Assay
Detecting apoptosis using annexin V and NucleoCounter® NC-3000™
- Ascertain if cells are in early or late-stage apoptosis/necrosis
- Fast, automated single cell analysis
- Standardized results – even between different users
- User-friendly protocol with predefined settings
- No calibration required
- Clear data presentation with Plot Manager feature
- Automated PDF reports
- Export data in FCS/ACS formats
Overview of the Annexin V Assay
Externalization, or translocation, of phosphatidylserine (PS) from the inner to the outer membrane leaflet happens in early apoptosis and precedes other apoptotic events such as loss of membrane integrity and DNA fragmentation.
Annexins are a group of cellular proteins that bind to phospholipids in a calcium-dependent manner. A member of this group, Annexin V, has proven to be a useful tool in detecting apoptotic cells since it has a high affinity for PS, and thus translocates with PS to the outer cell membrane.
Using fluorescently labeled Annexin V, the externalization of PS can easily be detected. Annexin V may also bind to PS on late apoptotic and necrotic cells but as the membrane integrity on these cells has been lost, they can be distinguished from early apoptotic cells using propidium iodide (PI). The PI dye is not membrane-permeable and is used to stain cells and DNA.
Using fluorescence microscopy and image analysis, the NucleoCounter® NC-3000™ advanced image cytometer automatically detects apoptotic cells based on PS externalization. Cells are stained with Hoechst 33342, PI and FITC-labeled Annexin V.
Hoechst 33342 stains the total cell population, while Annexin V stains apoptotic and necrotic cells. Early apoptotic cells exclude PI, while late-stage apoptotic and necrotic cells stain positive for both Annexin V and PI.
Results presented in plot manager
Jurkat cells were grown in the absence (upper row) or presence (lower row) of camptothecin (CPT). Cells were stained with Hoechst 33342, Annexin V-Fluorescein Isothiocyanate (FITC) conjugated antibody and propidium iodide (PI) and analyzed using the Annexin V Assay with the NucleoCounter® NC-3000™.
Scatter plots and histograms were obtained in the NucleoView™ NC-3000™ software. Quadrants (B, F) and markers (C, D, G, H) in the displayed plots were used to demarcate the various cell populations. In this example, CPT causes a significant increase of early apoptotic cells (marked as Annexin V positive and PI negative cells in the lower right quadrant, F).