T-cell numbers and function according to TREC⁺ T-cell status. (A-C) Absolute counts of CD3⁺ (A), CD4⁺ (B), and CD8⁺ (C) (on the y-axis) were plotted against TREC values (copies/1 × 10⁵ PBMCs; on the x-axis). There was a significant correlation between CD3⁺ T cells and TRECs (P = .003, r = 0.55); CD4⁺ and TRECs (P < .001, r = 0.79); and CD8⁺ and TRECs (P = .02, r = 0.43). (D) Counts per minute (cpm) of tritium-labeled thymidine incorporated into proliferating lymphocytes in response to phytohemagglutinin (PHA) stimulation (y-axis) were plotted against the TREC values (copies/1 × 10⁵ PBMCs; x-axis). There was a significant correlation between T-cell proliferation and TREC values (P < .001, r = 0.68).