Reciprocal Relationship Between Sleep and the Immune Response: A Survey

It is well known that sleep restriction or impairment results in an increase of the risk of get an infectious disease. As well, once a subject is sick due to an infectious disease, his sleep pattern changes completely. For a number of years these facts have been interpreted as the result of the alteration or lost of the main sleep function, the restoration of the defense system. Nevertheless, the experimental evidences to support this idea are surprisingly scarce. In a recent study on several species, a positive correlation was found between total sleep time and the number of circulating immune cells and, in addition, the species with longer sleep periods had reduced levels of parasitic infections. Experimental impairments of sleep, result in alterations in both the cellular and the humoral immune response. Early experiments on sleep restricted humans showed an increase of monocytes and natural killer (NK) cells, with a significant decrease of lymphocytes T. Concerning the immune humoral response, several cytokines have shown a close relationship with sleep. Some of them are capable of induce sleep when administered to specific regions in the brain. As well, some of them display significant changes when sleep is altered. Thus, it seems that sleep has an influence on the cellular and humoral immune response and, in turn, cytokines regulate the sleep pattern. The full understanding of this relationship could enable us to open new approaches in the therapeutic management of immune diseases. This paper reviews some of the most conspicuous data on these reciprocal influences.