P2X7-stimulated lymphocyte programmed cell death (PCD). Lymphocytes from New Zealand Black (NZB) mice, New Zealand White (NZW) mice and (NZB × NZW)F1 (NZB/W) mice were stained with anti-CD4APC and anti-CD8FITC, and were equilibrated with propidium iodide (PI). Panels show the mean percentage (± standard deviation, n = 5) of dead cells (those taking up PI) as assessed by flow cytometry before (t = 0), and at 15-min intervals subsequent to, stimulation of the P2X7 receptor with 2'-3'-O-(4-benzoylbenzoyl)-adenosine 5'-triphosphate. (a) CD4+ cells, and (b) CD8+ cells. NZB, open squares; NZW, open circles; NZB/W, open diamonds.