Nav: Home

Strong activation of anti-bacterial T cells linked to severe COVID-19

September 28, 2020

A type of anti-bacterial T cells, so-called MAIT cells, are strongly activated in people with moderate to severe COVID-19 disease, according to a study by researchers at Karolinska Institutet in Sweden that is published in the journal Science Immunology. The findings contribute to increased understanding about how our immune system responds against COVID-19 infection.

"To find potential treatments against COVID-19, it is important to understand in detail how our immune system reacts and, in some cases, perhaps contribute to worsening the disease," says Johan Sandberg, professor at the Department of Medicine, Huddinge, at Karolinska Institutet and the study's corresponding author.

T cells are a type of white blood cells that are specialized in recognizing infected cells, and are an essential part of the immune system. About 1 to 5 percent of T cells in the blood of healthy people consist of so-called MAIT cells (mucosa-associated invariant T cells), which are primarily important for controlling bacteria but can also be recruited by the immune system to fight some viral infections.

In this study, the researchers wanted to find out which role MAIT cells play in COVID-19 disease pathogenesis. They examined the presence and character of MAIT cells in blood samples from 24 patients admitted to Karolinska University Hospital with moderate to severe COVID-19 disease and compared these with blood samples from 14 healthy controls and 45 individuals who had recovered from COVID-19. Four of the patients died in the hospital.

The results show that the number of MAIT cells in the blood decline sharply in patients with moderate or severe COVID-19 and that the remaining cells in circulation are highly activated, which suggests they are engaged in the immune response against SARS-CoV-2. This pattern of reduced number and activation in the blood is stronger for MAIT cells than for other T cells. The researchers also noted that pro-inflammatory MAIT cells accumulated in the airways of COVID-19 patients to a larger degree than in healthy people.

"Taken together, these analyses indicate that the reduced number of MAIT cells in the blood of COVID-19 patients is at least partly due increased accumulation in the airways," Johan Sandberg says.

In convalescent patients, the number of MAIT cells in the blood recovered at least partially in the weeks after disease, which can be important for managing bacterial infections in individuals who have had COVID-19, according to the researchers. In the patients who died, the researchers noted that the MAIT cells tended to be extremely activated with lower expression of the receptor CXCR3 than in those who survived.

"The findings of our study show that the MAIT cells are highly engaged in the immunological response against COVID-19," Johan Sandberg says. "A likely interpretation is that the characteristics of MAIT cells make them engaged early on in both the systemic immune response and in the local immune response in the airways to which they are recruited from the blood by inflammatory signals. There, they are likely to contribute to the fast, innate immune response against the virus. In some people with COVID-19, the activation of MAIT cells becomes excessive and this correlates with severe disease."
-end-
This research was supported by the Swedish Research Council, the Swedish Cancer Society, the Swedish Heart-Lung Foundation, the Knut and Alice Wallenberg Foundation, Nordstjernan AB and Karolinska Institutet.

Publication: "MAIT cell activation and dynamics associated with COVID-19 disease severity," Parrot, T., Gorin, J. B., Ponzetta, A., Maleki, K. T., Kammann, T., Emgård, J., Perez-Potti, A., Sekine, T., Rivera-Ballesteros, O., the Karolinska COVID-19 Study Group, Gredmark-Russ, S., Rooyackers, O., Folkesson, E., Eriksson, L. I., Norrby-Teglund, A., Ljunggren, H. G., Björkström, N. K., Aleman, S., Buggert, M., Klingström, J., Strålin, K., and Sandberg, J. K., Science Immunology, online September 28, 2020, doi: 10.1126/sciimmunol.abe1670

Karolinska Institutet

Related Immune System Articles:

Memory training for the immune system
The immune system will memorize the pathogen after an infection and can therefore react promptly after reinfection with the same pathogen.
Immune system may have another job -- combatting depression
An inflammatory autoimmune response within the central nervous system similar to one linked to neurodegenerative diseases such as multiple sclerosis (MS) has also been found in the spinal fluid of healthy people, according to a new Yale-led study comparing immune system cells in the spinal fluid of MS patients and healthy subjects.
COVID-19: Immune system derails
Contrary to what has been generally assumed so far, a severe course of COVID-19 does not solely result in a strong immune reaction - rather, the immune response is caught in a continuous loop of activation and inhibition.
Immune cell steroids help tumours suppress the immune system, offering new drug targets
Tumours found to evade the immune system by telling immune cells to produce immunosuppressive steroids.
Immune system -- Knocked off balance
Instead of protecting us, the immune system can sometimes go awry, as in the case of autoimmune diseases and allergies.
Too much salt weakens the immune system
A high-salt diet is not only bad for one's blood pressure, but also for the immune system.
Parkinson's and the immune system
Mutations in the Parkin gene are a common cause of hereditary forms of Parkinson's disease.
How an immune system regulator shifts the balance of immune cells
Researchers have provided new insight on the role of cyclic AMP (cAMP) in regulating the immune response.
Immune system upgrade
Theoretically, our immune system could detect and kill cancer cells.
Using the immune system as a defence against cancer
Research published today in the British Journal of Cancer has found that a naturally occurring molecule and a component of the immune system that can successfully target and kill cancer cells, can also encourage immunity against cancer resurgence.
More Immune System News and Immune System Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: The Power Of Spaces
How do spaces shape the human experience? In what ways do our rooms, homes, and buildings give us meaning and purpose? This hour, TED speakers explore the power of the spaces we make and inhabit. Guests include architect Michael Murphy, musician David Byrne, artist Es Devlin, and architect Siamak Hariri.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

What If?
There's plenty of speculation about what Donald Trump might do in the wake of the election. Would he dispute the results if he loses? Would he simply refuse to leave office, or even try to use the military to maintain control? Last summer, Rosa Brooks got together a team of experts and political operatives from both sides of the aisle to ask a slightly different question. Rather than arguing about whether he'd do those things, they dug into what exactly would happen if he did. Part war game part choose your own adventure, Rosa's Transition Integrity Project doesn't give us any predictions, and it isn't a referendum on Trump. Instead, it's a deeply illuminating stress test on our laws, our institutions, and on the commitment to democracy written into the constitution. This episode was reported by Bethel Habte, with help from Tracie Hunte, and produced by Bethel Habte. Jeremy Bloom provided original music. Support Radiolab by becoming a member today at Radiolab.org/donate.     You can read The Transition Integrity Project's report here.