Annexin V/7-AAD staining in keratinocytes.

Annexin V/7-amino-actinomycin staining is a convenient way to discriminate early apoptosis from late apoptosis and necrosis. Early apoptotic cells express phosphatidylserines (PS) on the outer leaflet of the plasma membrane. PS can be stained by labeled annexin V. Late apoptotic cells and necrotic cells lose their cell membrane integrity and are permeable to vital dyes such as 7-AAD (DNA intercalator).