Apoptosis exposes MYHIIA and permits CLL subset 6 mAb reactivity. (A-B) Spontaneous apoptosis in Jurkat cells was revealed by propidium iodide (PI; red)–stained DNA in condensed nuclei. Apoptotic cells were costained under nonpermeabilizing conditions with (A) anti-MYHIIA antibody (green) or (B) CLL 068 mAb (green) and visualized by confocal microscopy (original magnification, ×600). Two representative cells from 6 independent experiments are shown with the average Pearson correlation coefficient (r) as a measure of colocalization. (C) Spontaneous apoptotic Jurkat cells were stained under nonpermeabilizing conditions with anti-MYHIIA (red) and CLL 068 mAb (green) and visualized by confocal microscopy (original magnification, ×600). Two representative cells from 3 independent experiments are shown with the average r. In all experiments (A-C), merges of red and green panels are shown (Merge; overlap in yellow-orange) and staining with secondary antibody alone was negative (not shown).