The hyporesponsive state of CD4⁺ T cells obtained early after ASCT is partially reversed by the depletion of CD4⁺CD25^bright cells and completely reversed by the addition of IL-2. FACS-sorted CD4⁺ T cells and CD4⁺ T cells depleted of CD4⁺CD25^bright T cells (CD4⁺CD25^- T cells) of 4 patients obtained 3 to 6 months after ASCT (A) and 3 healthy controls (B) were cultured in the presence of plate-bound anti-CD3, APCs, and with or without the addition of IL-2 (10 ng/mL). Proliferation was measured after 5 days by tritium incorporation.