ABSTRACT
Coordination between the immune and neuroendocrine system is crucial for mammalian immune response. Besides the well known cross-talk among hormones and cytokine at the level of immunecompetent cells, endocrine glands, and the central nervous system [1], the circadian temporization of the immune, endocrine, and nervous systems is relevant for a proper immune response. This interconnection is based on both positive and negative feedback loops, which regulate the timing of parallel and sequential events during immune responses. Lethargy, weakness, and decreased food intake show a circadian pro£le [2]. The effect of cytokines, such as tumor necrosis factor (TNF) and interleukin 1-β (IL1-β), responsible for the development of these effects, known as sickness behavior [3], show a rhythm pro£le [4-6].
