Figure 2. Analysis of in vivo kinetics of human CD4⁺ CD25^hi T cells.

Outline of protocol is shown in A. Subjects received 0.64 g/kg 6,6-D₂-glucose by half-hourly oral dosing for 10 hours. Blood samples were taken first during labeling, for analysis of deuterium content in plasma glucose, and second after labeling, to determine deuterium content in DNA. (B) Fraction of labeled cells (F, expressed relative to a labeling phase of 1 day) for each sorted cell population from 4 younger subjects (Y1–Y4) was determined. Open circles represent CD4⁺CD45RO⁺CD25^hi, filled circles represent CD4⁺CD45RO⁺CD25^–, and open squares represent CD4⁺CD45RA⁺ T cells. Error bars represent SD of triplicate gas chromatography mass spectrometry (GCMS) measurements (labeling of CD4⁺CD45RA⁺ T cells was too low to be detectable in individuals C16 and C17). Modeled proliferation and disappearance kinetics are best-fit curves as described in Methods. (C) The fraction of labeled cells in sorted T cell populations from t4 older subjects (O1–O2) and curve fits were analyzed and modeled in the same way.