Fig. 1.

Concept: Sleep supports the initiation of an adaptive immune response. The invading antigen is taken up and processed by antigen presenting cells (APC) which present fragments of the antigen to T helper (Th) cells, with the two kinds of cells forming an ‘immunological synapse’. The concomitant release of interleukin (IL)-12 by APC induces a Th1 response that supports the function of antigen-specific cytotoxic T cells and initiates the production of antibodies by B cells. This response finally generates long-lasting immunological memory for the antigen. Sleep, in particular slow wave sleep (SWS), and the circadian system act in concert to generate a pro-inflammatory hormonal milieu with enhanced growth hormone and prolactin release as well as reduced levels of the anti-inflammatory stress hormone cortisol. The hormonal changes in turn support the early steps in the generation of an adaptive immune response in the lymph nodes. In analogy to neurobehavioural memory formed in the central nervous system, the different phases of immunological memory might be divided in an encoding, a consolidation and a recall phase. In both the central nervous system and the immune system, sleep specifically supports the consolidation stage of the respective memory types. Modified from Lange and Born [71]