Correlation between TREC contents within CD4 and CD8 T-cell populations and age. Analysis was performed in 297 HIV-1-infected and 120 HIV-negative subjects ranging in age from 20 to 60 years. Continuous (HIV-negative) and dashed (HIV-1-infected) lines indicate best-fit linear regression curves, whereas r gives the Pearson correlation coefficient. TREC contents within purified CD4 (A) and CD8 (B) T-cell populations were determined as described in the “Patients, materials, and methods.”