In what is being called as a "big step" towards answering one of medical science's great questions, Scottish scientists have discovered genetic "brakes" which could slow down or stop diseases such as multiple sclerosis and cancer.
The findings by the researchers at the Roslin Institute could lead to new treatments and even cures for illnesses, which affect the immune system.
Professor David Hume, the director of the University of Edinburgh's Roslin Institute, has said that the findings have opened up a whole new field of scientific research, which would change the way vaccines were used and drugs were tested.
In the three-year study, international researchers focused on the immune system and examined the genes involved with white blood cells called macrophages.
They noticed that these cells, when healthy, cleanse the body of viruses and bacteria.
But, if they grow uncontrollably, they can turn against the body's own tissue to cause conditions such as Multiple Sclerosis (MS), arthritis and emphysema.
It was previously believed that such cell-growth processes were managed by a select group of master, or regulator, genes that give instructions to many other genes.
However, the new study, makes clear that there are, in fact, hundreds of regulator genes which all interact with each other to control cell development and growth.
This, according to scientists, helps to explain why people can develop the same disease in different ways, because of variations in different parts of their genetic networks.
They also said that if weak spots in these networks were identified, it would soon be possible to stop the growth of tumours, or enable the growth of healthy cells.
In addition, the researchers hoped that the new research could lead to treatments for the likes of myeloid leukaemia and arthritis.
The researchers said the findings offered up previously hidden information about the immune system and could ultimately help doctors understand why some cancer patients responded to immunotherapies while others did not.
"This research provides an incredible resource for the study of immunity and disease in humans and animals. This study has effectively shown us where the brakes are which could slow down or stop diseases like cancer and multiple sclerosis. We believe that this could lead to treatments and cures for many diseases of the immune system," the Scotsman quoted Hume as saying.