Deuterium incorporation by CD4 and CD8 cells. (A) Mean peak deuterium incorporation was significantly higher in HIV-infected patients receiving IL-2 (n = 18) for both CD4 and CD8 cell populations when compared with HIV-uninfected controls (n = 8) and HIV-infected patients who did not receive IL-2 (n = 9) (P < 0.001 for all comparisons, Student’s t test). Error bars represent the standard deviation. (B and C) Deuterium labeling kinetics in 2 HIV-infected patients who did not receive IL-2 (patients 20 and 22, Table 1) and an HIV^– volunteer (patient 30) (B) and in 3 HIV-infected patients who were long-term participants in intermittent IL-2 studies (patients 1, 2, and 4) (C). Patients 1 and 2 were long-term responders (see Figure 1 and Table 1), while patient 4 did not exhibit a CD4 count increase during IL-2 therapy. The continuous lines represent the fitting of the experimental data points (individual symbols) by the model equations. For the first 2 patients, the open symbol represents the percentage deuterium incorporation in cells obtained from a lymph node biopsy (at approximately 3 months). Time 0 is the beginning of the ²H-glucose infusion, which started 2 days after initiation of IL-2 treatment. (D) The probability density function (PD) of the normal distribution of log d multiplied by the total source of labeled cells (S) for the patients in C. The mean log decay rate constants (m_d) for CD4/CD8 cells for the patients are, respectively: patient (pt.) 1, –2.68/–1.68; pt. 2, –2.44/–1.44; pt. 4, 1.16/0.52. One log difference represents a 10-fold difference in half-life.