A study, published in the journal Immunity, has shown that the circadian rhythm controls the level of a gene vital to one's immune system and any disruptions to the cycle can lead one to illness.

The circadian rhythm, commonly referred to as body clock, is the self-sustained process, roughly 24-hour cycle in biochemical, physiological, or behavioral processes. It's been also widely observed in plants, animals, fungi and cyanobacteria.

Jet lag is resulted when the body gets out of synchronize with its surroundings after crossing time zones.

It has been known to us that there are variations in the immune system throughout the day. Now, the researchers are drilling down the root causes for details.

The researchers at the Yale University School of Medicine linked the gene TLR-9 to the circadian rhythm in mice.

The scientists showed that the amount of TLR9 produced is functioned and controlled by the body clock, and varied through the day. Immunizing the mice at the peak of TLR9 activity showed improved the immune response.

Prof Erol Fikrig, who conducted the study at Yale University, was quoted by the Daily Mail as saying: People intuitively know that when their sleep patterns are disturbed, they are more likely to get sick.

Fikrig added, Sleep patterns of patients in intensive care are often disrupted because of the noise and prolonged exposure to artificial light. It will be important to investigate how these factors influence immune system response.