Susceptibility to enhanced spontaneous apoptosis in vitro of T subpopulations according to CD45RO isoform expression. (A) A typical triple-color immunofluorescence analysis performed with the cells of UPN 440 and his bone marrow donor. The values in brackets are the percentages of apoptotic cells (DiOC₆(3)^low) within the CD45RO⁺ and CD45RO⁻ T-cell subpopulations. (B) Similar analyses performed with the cells of 6 other BMT patients and their corresponding bone marrow donors. The histograms show the means ± SD of individual determinations.