Rhythms of circulating T cell subsets. Mean (± SEM) of (A, E) naive (CD45RA⁺CD62L⁺), (B, F) central memory (CD45RA⁻CD62L⁺), (C, G) effector memory (CD45RA⁻CD62L⁻), and (D, H) effector (CD45RA⁺CD62L⁻) CD4⁺ (left) and CD8⁺ (right) T cells; n = 14. Rhythms with nocturnal peaks are more pronounced for naive T cells than for central memory and effector memory T cells. In contrast, effector CD8⁺ T cells peak during the day. Cosinor analysis of circadian rhythms was performed on data collapsed across conditions of a regular sleep-wake cycle and 24-hour continuous wakefulness (Table 1, rhythm characteristics). Adapted cosine curves are indicated for confirmed circadian rhythm. Shaded area represents bedtime.