[Circadian rhythm in cytokines].

The well-known human circadian rhythm (CR) in body temperature may be due to CR in endogenous pyrogens such as interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF). We, therefore, investigated the daily variation in spontaneous and LPS-induced monokine release by peripheral blood cells (whole blood assay) in 10 healthy volunteers. Spontaneous release of monokines (IL-1, IL-6, TNF) showed a simultaneous significant peak at noon, whereas LPS-induced release of IL-1 and IL-6 was strictly correlated with the CR in body temperature with its significant maximum at 8.00 p.m. Since LPS-induced release of TNF showed a significant peak at 4.00 a.m., interleukins and TNF seem to be independently regulated. CR in IL-1 and IL-6 release are suggested to be responsible for the CR in body temperature.