b'Chapter 3The health of the immune system is greatly influenced by our daily thoughts and our daily activities. How much sleep we do or dont get, how much exercise we do, whether we smoke, and how much alcohol we drink all significantly impact immune function. Sleep And ImmunitySleep is essential for the proper functioning of the immune system. Sleep-deprived individuals have decreased natural killer cell activity and decreased cellular immunity. Even a few nights of sleep deprivation can disrupt immune function. A pattern of insufficient and poor quality of sleep impairs nighttime secretion of cytokines, the messenger molecules that trigger a cell-killing attack by T-cells and natural killer cells. Sleeping stimulates the secretion of melatonin, a hormone released by the pineal gland. In addition to supporting deep sleep, melatonin also supports immune function. Melatonin has a number of critical immune-enhancing functions:Acts as a free radical scavenger and antioxidant.Protects cells (via free radical scavenging).Modulates immune activity (increases T-cell activity and production of immune-stimulating interleukins and cytokines).Decreases cancer cell growth.IMMUNITY5'