During cell apoptosis, inside of dying cells CADs cleavage the intact DNA into fragments exposing 3′-hydroxy ends which can be extended with poly-dUTP by terminal deoxynucleotidy transferase (TdT) and shown as TUNEL positive. Subsequently, the DNA fragments are then digested by DNase II, either in dying cells or in engulfing cells, to yield products with 5′-hydroxy ends and 3′-phsophate ends which are unable to be reacted with tdt and shown as TUNEL negative. In the present study, a ToLFP was employed to directly label the 5′-hydroxy ends and shown as ToLFP positive.