Mevastatin-treated differentiating monocytes are particularly susceptible to apoptosis. After 24 h of statin treatment monocytes still constituted a single, viable cell population (panel A, black arrow). By 48 h this viable monocytic population had decreased in size and a second population of smaller, annexin V-positive cells had appeared (B). By 72 h the majority of monocytes were undergoing apoptosis (C). Conversely, peripheral blood lymphocytes (white arrow) remained largely viable throughout the observation period. Results shown here are representative of 18 experiments (three per individual).