A good night's sleep really can be the best medicine.
Scientists have discovered that sleep improves the ability of immune cells to hit their targets and fight off infection.
While sleep helps to boost the body's defences, chronic stress may make it more vulnerable to illness, the study suggests.
The German team investigated sticky proteins called integrins that are released by T-cells, a key element of the immune system.
Integrins allow T-cells to attach to a target, such as a cell infected by a harmful virus, and kill it.
T-cells taken from sleeping volunteers showed significantly higher levels of integrin activation than those from study participants who stayed awake all night, the researchers said.
The different response is thought to be linked to dipping levels of the hormones adrenaline and prostaglandin during sleep.
In tests, both hormones were shown to suppress integrin activation.
Several hormones, including those that suppress integrin activation, are known to be linked to cancer, malaria infection, hypoxia (oxygen starvation) and stress, said the researchers.
The study, published in the Journal of Experimental Medicine, could aid the development of new therapies to improve the fighting ability of T-cells, they said. This could be especially useful in forms of cancer immunotherapy that involve prompting T-cells to target and destroy tumour cells.