Number and function of circulating human antigen presenting cells regulated by sleep

There is evidence that sleep facilitates the adaptive immune response to infectious agents and, thereby, supports immunologic memory. The effect might be attained by sleep-induced changes in the number and function of dendritic cells (DCs), which play a key role in the initiation of the immune response. This study aimed to dissociate effects of sleep and circadian rhythm on circulating numbers of DC precursors, ie, CD14+CD16- and CD14(dim)CD16+ monocytes, myeloid dendritic cell precursors (pre-mDC), and plasmacytoid dendritic cells (PDC) and on 2 key cytokines produced by these cells, ie, interleukin (IL)-12 and interferon (IFN)-alpha.

In a within-subject cross-over design, human subjects were examined on 2 occasions, ie, during a normal sleep-wake cycle and during 24 hours of wakefulness. Blood was sampled every 1.5 hours during nighttime and every 3 hours during daytime.

Experiments took place under controlled laboratory conditions.

Twenty-seven healthy men aged between 18 and 30 years.

Compared with wakefulness, sleep was associated with a striking increase in the number of pre-mDC producing IL-12, which is a main inducer of Th1 responses. In addition, sleep slightly decreased PDC and also T cell counts but did not affect IFN-alpha production by PDC. Sleep, however, substantially decreased numbers of CD14(dim)CD16+ monocytes, probably reflecting increased margination of the cells upon a sleep-related drop in catecholamine release.

Our data identify pre-mDC producing IL-12 as a basic target of sleep that is most closely related to mature APC function and whereby sleep can effectively enhance adaptive immune responses.