Cell-cycle analysis of lymphocytes treated with anti-Fas MoAb (CH11). Flow cytometric analysis of nuclei of lymphocytes stained with propidium iodide (N = 60). Hypoploid peak reflects the percentages of apoptotic cells. X axis, DNA content; Y axis, cell number. The histograms of PBMCs from normal donor (top) and HIV⁺ patient (bottom) showed the following: control (untreated lymphocytes), treated with Fas triggering antibody (CH11), treated with Fas blocking MoAb (ZB4). (⋅⋅⋅) The apoptotic peak; ( — ) the G1 phase; (- - -) the G2 phase of cell cycle.