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. When patients with static and active vitiligo were compared, those with the static form had increased natural killer cell activity at all times except noon, wherease those with active form had increased natural killer cell activity only at 0600 and 1800. These changes shifted the acrophase of the circadian rhythm of each group. Indeed, by cosinor analysis, both patients with vitiligo and normal controls had similar circadian rhythms, but the acrophase was shifted from 0602 in control subjects to 0435 in the ten patients with vitiligo. The acrophase in the six patients with active vitiligo was found to be closest to that of normal controls (0508). These findings indicate that natural killer cell activity abnormalities are more marked in the static rather than in the active form of vitiligo.