T cell subpopulations in vitiligo: a chronobiologic study.

The circadian rhythms of helper (CD4) and suppressor (CD8) T cells from the peripheral blood of 12 vitiligo patients (seven with active disease, five with static) and 12 healthy control subjects were studied. Patients with active vitiligo had a lower percentage of CD4+ cells than did control subjects at 0000 hours and at 0600 and 1200 hours; there were no differences between these values in patients with static vitiligo and those in control subjects. The percentage of CD8+ cells were lower at 1200 and 1800 hours in both active and static vitiligo patients than in control subjects.

Circadian rhythm of natural killer cell activity in vitiligo.

Ten patients with vitiligo, either in the active (six cases) or static (four cases) phase, and twelve healthy control subjects were studied with a standard cytotoxicity assay to evaluate the circadian rhythm of natural killer cell activity from peripheral blood mononuclear cells. The natural killer cell activity was measured at the zero, sixth, twelfth, and eighteenth hours of the day. The results demonstrated that patients with vitiligo had significantly higher natural killer cell activity compared with normal controls.

Plasma melatonin levels in psoriasis.

Melatonin is synthesized and secreted by the pineal gland. A daily rhythm of melatonin secretion, with high plasma values during the dark period, has been found in all vertebrates studied so far. In psoriatics, several hormones, including GH and prolactin, have altered chronobiology, and some studies in humans suggest that melatonin affects the levels of GH and prolactin.