After just one night of insufficient sleep, your immune system stops functioning properly. This is evident from a now-classic human study published by American psychoneuroimmunologists in 1994 in Psychosomatic Medicine.

Study
The researchers, affiliated with the University of California and the San Diego Veterans Affairs Medical Center, took a small amount of blood from 23 healthy men in the morning.

On another day, they woke the men at 3:00 a.m. They were not allowed to go back to sleep between 3:00 a.m. and 7:00 a.m. Early in the morning, the researchers took another small amount of blood.

The researchers extracted the Natural Killer cells from the subjects' blood and exposed them to K562 cancer cells. They then measured how many cancer cells the Natural Killer cells could eliminate.

Results
In 18 of the 23 men, the ability of their natural killer (NK) cells to eliminate cancer cells (lytic activity) decreased. This ability decreased by an average of 28 percent due to sleep deprivation.

NK cells are a prominent part of the innate immune system. When healthy cells turn into cancer cells, when bacteria invade the body, and when viruses infect cells, the innate immune system is the first to spring into action. A healthy innate immune system can, with a bit of luck, nip countless health problems in the bud.