In the post–T-cell depletion period the increased susceptibility to apoptosis affects both the naive (CD4⁺ CD45RA⁺) and the memory (CD4⁺ CD45RA⁻) T-helper cell population.

PBMCs of control samples (upper panels) and of patient samples (lower panels) were cultured in medium without the presence of T-cell stimulants (resting cultures) as described. At 24 hours of culture, T-helper cells were identified by anti-CD4 and gated and assessed for expression of CD45RA. The CD4⁺CD45RA⁺ and the CD4⁺CD45RA⁻ populations were gated and separately analyzed for binding of annexin V. The percent annexin V binding cells were as follows: control CD4⁺ cells, 4%; control CD4⁺ CD45RA⁺ cells, 1%; control CD4⁺CD45RA⁻ cells, 7%; patient CD4⁺ cells, 19%; patient CD4⁺CD45RA⁺ cells, 18%; patient CD4⁺ CD45RA⁻ cells, 19%. The patient cells were obtained from a 12-year-old girl with Ewing sarcoma (patient 10) 3 months after completion of conventional high-dose chemotherapy. CD4⁺CD45RA⁺ cells, 60/μL.