Immune reconstitution of T cells (CD3⁺, CD4⁺, CD8⁺, CD4⁺CD45RA⁺), B cells (CD19/20⁺), and NK cells (CD56⁺) while receiving ERT. Patients included those who received ERT only (n = 9) and patients who received ERT before first definitive cellular therapy, censored at the time of starting HCT or GT (n = 65). The x axis refers to the time after starting ERT. Numbers below each time point indicate the number of patients with evaluable data. (A-F) Absolute numbers of cells in each lymphocyte subset at ADA diagnosis (DX) and at different time points after initiation of ERT. By comparison, the 10th percentile of lymphocyte subsets in healthy 1- to 2-year-old children are as follows (all ×10⁶/L): CD3⁺, 2100; CD4⁺, 1300; CD8⁺, 620; CD4⁺CD45RA⁺, 1000; CD19 B cells, 720; CD56 NK cells, 180.⁵⁷ (G) Proportion of patients able to discontinue immunoglobulin replacement after ERT. (H) T-cell proliferative responses to phytohemagglutinin (PHA) improve for most but not all patients with ADA SCID after 6 months of ERT. Horizontal line, median; thick vertical bars, interquartile range; thin vertical lines, range.