Prolonged T lymphopenia and relative expansion of B cells and NK cells after CBT. T cells (CD3⁺CD4⁺ and CD3⁺CD8⁺), B cells (CD19⁺), and NK cells (CD16⁺ and/or CD56⁺) were prospectively measured by multiparameter flow cytometry on fresh samples. At baseline and after CBT, CD4⁺ and CD8⁺ T cells were relatively reduced, whereas early B-cell and NK-cell recovery was evident. Surviving CB transplant recipients demonstrated rebound of CD4⁺ and CD8⁺ T cells at later intervals after transplantation. Horizontal lines depict normal values for healthy stem cell transplant donor previously studied by Storek et al.²⁵  Error bars represent SEM.