Apoptosis induced by gemcitabine and rituximab. Cells treated as in figure 2, except with 10 nM gemcitabine, then stained with annexin V and propidium iodide. Top left panel (A) is total annexin V positive cells. Top right panel (B) shows early apoptosis (annexin+/PI-, left) and late apoptosis (annexin+/PI+, right). A typical dot plot (C) is also shown.