Sleep and Immunity

Sleep is considered an important modulator of the immune response. Thus, a lack of sleep can weaken immunity, increasing organism susceptibility to infection. The function of sleep in altering immune responses must be determined to understand how sleep deprivation increases the susceptibility to viral, bacterial, and parasitic infections. There are several alterations in the immune system after reduced sleep, such as impaired mitogenic proliferation of lymphocytes, decreased HLA-DR expression, the upregulation of CD14+, and variations in CD4+ and CD8+ T lymphocytes, which have been observed during partial sleep deprivation. Also, steroid hormones not only regulate sexual behavior but also influence sleep. Thus, we hypothesize that sleep and the immune–endocrine system have a bidirectional relationship in governing various physiological processes, including immunity to infections. This chapter discusses the evidence on the bidirectional interaction between sleep and immune system. Because sleep is essential in the maintenance of homeostasis, immune system changes must be adapted to elicit changes in sleep patterns and other physiological parameters during the immune response to infections to which the organism is continuously exposed.