Calbiochem® Annexin V-FITC Apoptosis Detection Kit II is a non-isotopic system that can be used to detect phosphatidylserine on the outer leaflet of the cell membrane of apoptotic cells using flow cytometry or fluorescence microscopy.

The Calbiochem® Annexin V-FITC Apoptosis Detection Kit II utilises annexin V conjugated to FITC to bind to phosphatidylserine on the outer surface of cells undergoing apoptosis. Fluorescence is then detected by flow cytometry or fluorescence microscopy. Since membrane permeabilisation is also observed in necrosis, necrotic cells will also bind Annexin V-FITC. Propidium iodide is included to help distinguish between viable, early apoptotic, and necrotic or late apoptotic cells. Necrotic cells will bind Annexin V-FITC and stain with propidium iodide while propidium iodide will be excluded from viable (FITC negative) and early apoptotic (FITC positive) cells. In the absence of phagocytosis final stages of apoptosis involve necrotic-like disintegration of the total cell, thus cells in late apoptosis will be labeled with both FITC and propidium iodide.