In a study of narcolepsy patients, researchers at the University of Copenhagen have made an important discovery that could help pave the way for improved treatment of the chronic condition.
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The team found that the patients had autoreactive cytotoxic CD8 T cells in their blood, providing important new evidence that the condition is an autoimmune disease.
Scientists had already suspected that narcolepsy may be autoimmune in cause, but this new study, published in the journal Nature Communications, offers new proof that this hypothesis is correct.
“We have found autoreactive cytotoxic CD8 T cells in the blood of narcolepsy patients. That is, the cells recognise the neurons that produce hypocretin which regulates a person's waking state. It does not prove that they are the ones that killed the neurons, but it is an important step forward. Now we know what the cells are after,” says study author Birgitte Rahbek Kornum.
When immune cells are autoreactive, they recognize the body’s own cells as targets for attack, as if they were invading bacteria or viruses. The term cytotoxic refers to their ability to kill the cells they target. Generally, in narcolepsy patients, the neurons that produce hypocretin have been destroyed.
In 2018, researchers discovered autoreactive CD4 T cells in narcolepsy patients, which provided the first real evidence that narcolepsy may be an autoimmune condition. However, for the immune system to kill cells such us the hypocretin-producing neurons, CD4 T cells and CD8 T cells usually have to work together.
“Now we have provided more, important proof: that CD8 T cells are autoreactive too,” says Kornum.
For the study, the team compared blood samples from 20 narcolepsy patients with those taken from 52 healthy controls. The researchers found that almost all of the samples from the narcolepsy patients had autoreactive CD8 T cells.
Kornum says it is likely that studies will now focus more on treating narcolepsy with medications that allay the immune system. This has already been tried, given that scientists already suspected that the condition is autoimmune.
However, “now that we know that it is T cell-driven, we can begin to target and make immune treatments even more effective and precise,” concludes Kornum.