The staining procedure involves incubating cells with Annexin V conjugated to a fluorochrome, such as FITC or PE. In early apoptotic cells, phosphatidylserine is exposed on the cell surface, allowing Annexin V to bind. By using flow cytometry or microscopy, researchers can detect the fluorescent signal, which indicates the presence of apoptotic cells. Often, a viability dye like propidium iodide is used alongside Annexin V to differentiate between early apoptotic, late apoptotic, and necrotic cells.
